London Loop 15: Hatch End – Borehamwood

Caesar's Pond, Stanmore Common, one of the original 'stony meres' that gave the locality its name.

YOU’LL FIND TWO ANCIENT COMMONS AND SEVERAL ARTIFICIAL LAKES with stories to tell, alongside reminders of the entertainment industry, as the London Loop continues to meander along the London-Hertfordshire boundary. W S Gilbert, half of one of the Victorian era’s most successful creative teams, met an unexpected end at Grimsdyke Lake on Harrow Weald Common. Brewers Lake on Stanmore Common is a remnant of a vanished local industry, while Aldenham Reservoir, built by prisoners of war, is now the centrepiece of a more contemporary story about the use and misuse of public space. Other highlights are an ancient earthwork and the command centre of the Battle of Britain. The walk ends at the ‘British Hollywood’ of Elstree – or should that be Borehamwood?

This is a single long Loop section that could be split at several points, passing relatively close to Stanmore Underground station at the end of the Jubilee Line, although some of the bus stops are outside the TfL zone and Travelcards, Oyster and Contactless might not be valid.

Update November 2017. While I'd recommend sticking to the official London Loop route as described here if walking the trail for the first time, there are a couple of alternatives worth knowing about. You can start at Carpenders Park station and follow a pleasant woodland path along a stream to join the Loop at Mutton Wood. In Harrow Weald Common there's a shortcut that doesn't involve crossing the road to the Old Redding Viewpoint, and there's also a fairly long but very pleasant link to Stanmore halfway along, via Stanmore Country Park. Read more here.

Carpenders Park

As mentioned at the end of the previous section, the Loop bounces away from suburbia at Hatch End, roughly northwards on a fenced path with open meadows on the left, and a playing field and then an excrescence of the Pinnerwood Park estate on the right. Across another meadow, it reaches and then parallels the West Coast Main Line railway, discussed in the last section. Converging with the railway, you’re once again briefly leaving London and re-entering South Oxhey in Hertfordshire’s Three Rivers District. Hidden in the undergrowth of the railway embankment here is a coal post of a different and much larger design than the ones we’ve already encountered, but it’s behind the railway fence and hard to spot from the path. It dates from 1851 and was moved here ten years later following changes to the tax boundary.

The Loop follows Little Oxhey Lane across the railway over a historic bridge that dates from before the area was built up, as demonstrated by its inadequate width: the trail uses an additional footway which has been bolted on more recently. On the other side of the tracks, in more ways than one, is Carpenders Park, developed in the 1930s, a little earlier than neighbouring South Oxhey, and by private developers rather than the London County Council. So it’s always had a more upmarket reputation compared to its neighbour, undoubtedly reinforced by the way the railway so decisively separates them: the only links besides the one the Loop uses are several pedestrian subways around Carpenders Park station, about a kilometre to the north.

The Loop runs alongside neat houses set slightly back from the road, and passes a small green space, Romilly Drive Open Space. Walking along the edge of this unremarkable patch of green, you’ll enter the designated area of Watling Chase Community Forest, a gradually improving zone of green space straddling London’s northern boundary which I introduced on the way from Kings Langley to St Albans on the London Countryway. The trail stays within the Forest for the rest of this section and for nearly all of the next.

You pass a big garden centre to reach Oxhey Lane, once a winding country lane but now an important road link between Harrow and Watford. The former core of the old Carpenders Park estate is a little along the lane to the left here: the site of Carpenders mansion, later known as Highfield and demolished in 1960 to make way for married quarters for USAF personnel stationed at RAF South Ruislip nearby, which in turn were swept away in the late 1990s. Close by is Carpenders Park Lawn Cemetery, opened in 1954 and now shared between the London Boroughs of Brent and Harrow and Three Rivers council.

Across the busy road, the Loop glances the edge of a strip of ancient semi-natural woodland known as Mutton Wood, now managed as a local wildlife site. A track through rough ground beside the wood has been much improved in recent years, though still suffers from fly tipping. Then there’s the first golf course on today’s section, Grim’s Dyke Golf Club, created on former farmland by Hatch End residents in 1910. Its land now straddles both Hertfordshire and London.

Three boundaries meet where the path reaches a hedge on the left and passes to the left of a clump of trees. You’ll see that on the other side of the hedge, where there’s another golf course, a second hedge joins at right angles. This is the London boundary: the adjoining hedge would originally have continued straight across your path, but it’s been removed for the convenience of golfers so you can walk back into London unhindered. But the hedge you’ve been following is also a boundary, dividing two Hertfordshire districts: Three Rivers, on your side, and Hertsmere, on the other.

Grim’s Dyke

The mysterious Grim's Dyke, possibly a Celtic boundary feature.

You’ll soon find yourself walking on a hedged track where you encounter a more significant and curious boundary feature identified by a plaque just before a junction with a road. This is Grim’s Dyke, also known as Grim’s Ditch, an ancient linear earthwork consisting of an earth bank and a parallel ditch that stretch for some 3 km from Harrow Weald Common southwest to Pinner, possibly extending into Ruislip. Originally it might have been still longer, but substantial sections are long lost. If you followed the station link at Hatch End you will have already crossed its line, along Grimsdyke Road, but at that location there’s nothing to be seen on the ground. Here, it’s clearly visible: you’ll need to keep a lookout as it’s overgrown with trees, but you can see the metre-high earth embankment on both sides of the track, which appears to have sliced through it.

At this point, the Loop dodges left into the woods, running along the top of the embankment itself. To your right, on the south side of the bank, is the ditch, more recently turned into a decorative canal feature in the gardens of Grimsdyke House.

The Dyke is one of those many large-scale landscape features, both natural and artificial, once considered supernatural, and probably malevolent, in origin. Grim is an Anglo-Saxon term for a devil of goblin, and the earthwork itself has traditionally been given a Saxon origin, although many now think it’s rather older. It’s never been definitively dated, but archaeological finds in the vicinity, including a 1st century fire hearth uncovered during redevelopment of the house in 1979, suggest the early Roman period.

At that time, the Catuvellauni were attempting to expand their territory in the face of Roman power, so the structure might have played a role in this process. Its exact purpose is also unknown. This is high ground, on a ridge between the river Pinn to the south and the Hartsbourne stream to the north, so the ditch may have been defensive. But neither is it especially substantial, so it could just have marked an important boundary.

The land you’re now crossing, Grimsdyke Open Space, once part of Harrow Weald Common, was bought by artist Frederick Goodall in 1856, who began creating gardens and woods as a setting for a planned house, finally built in 1871 by the architect Richard Norman Shaw. At the architect’s suggestion, the name was changed for a while to the less foreboding Graeme’s Dyke, but was changed back by a celebrated new owner in 1890: the lyricist and dramatist William Schwenck Gilbert (1836-1911), one of the most prominent figures in the popular culture of his day.

Gilbert was already a successful playwright, director and comic poet when in 1869 he was introduced to the composer Arthur Sullivan. Between 1875 and 1891, the pair collaborated on a string of enormously successful comic operas in a highly distinctive style which are still regularly performed to enthusiastic audiences today, including The Pirates of Penzance (1878), The Mikado (1885) and The Gondoliers (1889). Many of them were premiered at the Savoy Theatre in the Strand, which impresario Richard D’Oyly Carte opened in 1881 specifically for that purpose.

Gilbert bought Grimsdyke just as his working relationship with Sullivan and D’Oyly Carte was breaking down. Both he and his collaborator were brilliant but difficult men who, as they advanced in age, grew increasingly frustrated that their light-hearted output enjoyed much greater success than their more serious work. They briefly reconciled and collaborated again in 1895 and 1896, but the magic had gone and the results enjoyed only moderate success.

Gradually Gilbert withdrew from theatre work and spent more time at Harrow Weald, continuing to improve the house and its grounds: he even became the inaugural president of the golf club. Climbing down from the dyke and working your way through banks of rhododendrons first planted for Goodall, you’ll soon find yourself beside Gilbert’s most significant and, as things turned out, most fateful addition, a 6,000 m2 boating lake complete with rock cascade and artificial island.

Grimsdyke Lake, built by W S Gilbert, who died in its waters

Gilbert personally supervised the digging of this lake in 1900 and was delighted with the result. On 29 May 1911, a teenage visitor, Ruby Preece, lost her footing while swimming in the lake and called for help. Gilbert plunged in to save her, but had a heart attack while in the water and died. His grieving widow Lucy ordered the lake drained, and so part of it has stayed since.

Preece, incidentally, survived the incident to become the artist, model and Bloomsbury Group associate Patricia Preece, second wife of tortured artist Stanley Spencer, whom we encountered at Cookham on the London Countryway – although she also maintained a long-term relationship with a female partner, Dorothy Hepworth.

Lucy Gilbert, 11 years younger than her husband, died in 1936 and the house became a sanatorium for tuberculosis patients. Part of it was used by the government for secret work during World War II, allegedly as a backup site for the codebreaking centre at Bletchley Park. The estate fell into the hands of Harrow Council when the sanatorium closed in 1963, and eventually the council rented out the house for conversion into a hotel in 1970, while retaining much of the grounds as a public park. Today, the lake is a peaceful, leafy place with a unique atmosphere, silent about the tragedy that unfolded there. You’ll only catch glimpses of the mock-Tudor house as you pass through the site, though you could detour up the drive, further along the route, for a better view. If you’re feeling flush, you could even spend a night: it’s still a hotel, one of the few on the Loop, now known as the Best Western Plus Grim’s Dyke Hotel.

Harrow Weald Common

Harrow Weald Common near Grimsdyke House: note the uneven surface resulting from gravel extraction.

The Loop emerges from the rhododendrons and conifers to track another earth bank, which once divided the more formal space around the house, on your left, from the more natural woodland of Harrow Weald Common on the right. These woods are a remnant of the Forest of Middlesex, a substantial tract of the near-continuous wildwood that had once carpeted prehistoric Britain. In the 1150s, the forest stretched northwards from the City of London boundary at Houndsditch for around 19 km to the edge of Hertfordshire, and was considered City property, with Londoners entitled to hunt there. It was officially ‘disafforested’ by Henry III in 1218 and the land was split between numerous individual property holders, but some of it remained thickly wooded and uncultivated for many more centuries.

This steep ridge with its poor, gravelly soil, rising to 145 m, eventually became the common lands of the Weald, originally a sprawling area of woodland and cottages which gave rise to a small hamlet on the lower ground to the south. The name is from Anglo-Saxon wald, a wooded upland: the designation ‘Harrow Weald’ only appeared in the later 18th century and some locals still call the place simply ‘Weald’ today. Inclosure took place in a piecemeal fashion: by 1759 the common extended to 300 ha and by 1817 it had been reduced to 277 ha. Land was not only taken for farming and housing but for industries like brickworks. But commoners continued to exercise their traditional rights, including grazing pigs and gravel extraction. The latter was particularly vigorously pursued and its effects are still evident today in the undulating floor of the woods.

An 1886 proposal to sell the remaining common lands for development was defeated by local opposition and in 1899, following concern about the impact of gravel extraction, an Act of Parliament set up a board of conservators to protect what remained. In 1965 the freehold passed to Harrow Council who now appoint all the conservators.

The Loop emerges on a road, once a meandering track along the top of the ridge and known by the picturesque name of Old Redding, from an obsolete word meaning a woodland clearing. Directly opposite is a car park and picnic site, the Old Redding Viewpoint, and even though our route heads back into the woods on the north side of the road a little further on, it’s well worth crossing and walking ahead for a few steps. It's possible to avoid the road and walk closer to Grim's Dyke House by staying within the common, if you don't mind missing out the view.

View from Old Redding Viewpoint

The land falls away as steep meadows beneath your feet, leaving a clear view south. Harrow on the Hill, topped with its church and school buildings, is the most prominent feature nearby: we’ll visit it on the Capital Ring. You’ll also see other local hills like Horsenden Hill, landmarks like Wembley Stadium in the distance and, off to the west, the planes landing and taking off at Heathrow. At 137 m, it’s the second-best view on the Loop, after Addington Hills on section 4, to which it provides a northerly complement on similar geology.

Returning to the road, you’ll note the hotel drive with its Grade II-listed lodge on the north side, and, right next to the car park, a picturesque whitewashed pub with the curious name The Case is Altered. A surprising number of pubs in England share this name, which derives from a 16th century legal set phrase, used by Ben Jonson as the title of a 1599 play. As applied to pubs, it could commemorate a change in the legal circumstances of the landlord or the local community. Among the alternative, less plausible, explanations is that it’s a corruption of la casa alta, Castilian for ‘the high house’ – which would at least seem appropriate to the airy setting here.

It’s a little surprising to find the pub still functioning (at the time of writing at least) in this isolated spot. When it was built around 1800, a cluster of cottages lined Old Redding, housing workers at the nearby brickworks, and the locality was known as the City, which must have seemed ironic even then. Nearly all are gone: several have been knocked together into one large house, while the car park now occupies the site of others. The old brickworks is now largely a garden centre just a little further along the lane, with its former use recalled in the name of a house, the Kiln. The locality name survives in the section of common the Loop now enters, which is known as The City Open Space.

Cottage originally attached to Grimsdyke House.

Through the woods to the right is a fenced-off area of common that’s designated as a Site of Special Scientific Interest (SSSI) particularly for its geological importance: the exposed gravels which cap the London clay here were deposited during the last glacial period. Further on is an unexpected cluster of cottages on the edge of wood: the more distinctive ones, on the left, were originally servants’ quarters, dating from the development of Grimsdyke House.

The trail now bends east along the woodland edge, crossing several streams that drain down the north-facing slope into the Hartsbourne and then the Colne. Then it crosses the end of a tree-lined path, Len’s Avenue, so-called because it was planted by Leonard Renery, Keeper of the Common between 1961 and his death in 1996. Back through the woods, you emerge on Common Road, which was cut through the trees to link Watford and Harrow in 1759. Across it, the trail enters a rather different but arguably even more historically significant green space.

Bentley Priory

View through the fence to Bentley Priory, command centre for the Battle of Britain, with its distinctive clock tower,

Sometime in the 12th or 13th centuries, a cell of Augustinian friars founded a priory high on the ridge to the northeast of Harrow, known as Bentley, probably derived from an Anglo-Saxon term meaning a clearing amid bent or rough grass. Some sources claim it was established by politician and lawyer Ranulf de Glanvill, who later became Chief Justiciar of England, in 1170. It was always a small community dependent on the priory of St Gregory, Canterbury, and it seems that by 1536, when it was dissolved in Henry VIII’s reforms, it was simply tenanted out as a source of income. After the dissolution it was given to Thomas Cranmer, Archbishop of Canterbury, who was forced to give it back when he fell out of favour with the king in 1542.

The property passed through several hands before being bought in 1766 by James Duberly, who demolished the old priory buildings, which probably stood some way down the slope in the southern part of the site, near where Priory House, a 16th century timber-framed farmhouse, still stands today. He replaced these with a new mansion at the top of the ridge, which, under its next owner John Hamilton, the Marquess of Abercorn, was extended and refurbished in 1788 to designs by the renowned architect John Soane. Although altered several times since, this building still stands today and is clearly visible from the Loop.

Hamilton managed the grounds as private parkland, including a deer park, and welcomed a starry cast of eminent people to the estate, among them prime minister William Pitt the Younger; military commander Arthur Wellesley, the Duke of Wellington; actor Sarah Siddons; author Walter Scott; and Emma Hamilton, later the lover of Admiral Horatio Nelson.

The priory had several further private occupants, including Queen Victoria’s aunt Queen Adelaide in the last year of her life between 1848-49. Engineer and building contractor John Kelk, responsible among other things for building the Albert Memorial in Hyde Park, added one of the most prominent architectural features, the clock tower, after he bought the estate in 1863. Between 1882 and 1908 it was a hotel, then a girls’ boarding school, neither of which were particularly successful.

The priory’s period of greatest fame was yet to come. In 1926, the site was split, with a few pockets of land sold for development, the bulk of the parkland taken on as green belt by Middlesex County Council, and the house and its immediate surroundings sold to the Air Ministry for a sum believed to be £25,000. The ministry installed the newly-formed Royal Air Force (RAF) in the house, and in 1936 it became the headquarters of RAF Fighter Command. So it was from here that Air Chief Marshal Hugh Dowding, later Baron Dowding of Bentley Priory, commanded the successful air defence of the UK in the 1940 Battle of Britain, the first important defeat for Nazi Germany. As such, although it was never an airfield, it’s one of two key World War II-related sites on the Loop, alongside Kenley in section 4.

The RAF stayed until 2008, although after 1968 used the site primarily for administration and training. Nonetheless, when I first walked this way in the 1990s, the tall fence separating the buildings from the parkland was surmounted by surveillance cameras and liberally dotted with Ministry of Defence warning notices. It’s currently in the process of being redeveloped as private housing, with the welcome inclusion of a museum run by the Bentley Priory Battle of Britain Trust, opened in 2013. Despite the lowering of security concerns, there’s still no direct connection between the green space and the buildings, so if you want to visit, you’ll need to detour along Common Road.

The parkland, meanwhile, eventually passed into the hands of the present-day Harrow council, though it’s largely managed by a voluntary group, the Harrow Nature Conservation Forum, part of the Harrow Heritage Trust. Thanks to its steep geography, its poor soils and its preservation as an 18th century country park through to the early days of the Green Belt, it’s one of the most expansive wild sites within London, with a patchwork of environments including ancient woodland and unimproved grassland that has never been ploughed and fertilised. It’s now a designated Local Nature Reserve and, by virtue of its species diversity, the only biological SSSI in the borough.

The Shard and other London landmarks
from Bentley Priory Nature Reserve

The Loop follows a narrow concrete path through the nature reserve, oddly reminiscent of 1940s aviation though of course it has no link to the RAF site. The sturdily fenced area to the left just after the road is Glenthorne, originally the site of a house of the same name which was requisitioned in 1940 as a proposed extension to the Priory complex. This was never built, and the land has remained undisturbed ever since. It may eventually become part of the reserve, or a city farm. Later there’s a World War II pillbox on the left.

The path runs along the ridge just below the house through an area known as Spring Meadow. There are good views of the historic buildings through the fence on the left, and rough grassland that tumbles down to reveal wide views through gaps in the trees, including all the tall landmarks in the City of London. You’ll also catch a glimpse of an ornamental lake, named Summerhouse Lake after the structure on its artificial island, where Walter Scott is said to have worked on the final revisions to his epic poem Marmion in 1807.

Then the surroundings turn notably scrubbier, with tough grasses and patches of gorse that give this area its name Furze Field. A junction of paths with interpretation boards and a Loop fingerpost seem like they could be in the middle of some remote heath, but you’re soon among the big and expensive houses that line the private streets of Priory Drive and Priory Close, on one of the pockets of priory land developed in the 1920s.

London Loop path junction in Bentley Priory Nature Reserve.

Stanmore Common

The track north from the Bentley Priory fingerpost out of the site follows the old parish boundary between Harrow and Stanmore, which ran through the priory site. The Loop definitively enters Stanmore when it turns east along Priory Drive. The parish, its name meaning a stony pond or lake, was part of the large areas of land granted by the Mercian king Offa II to St Albans Abbey on its foundation in the 790s, some of which we walked through in the previous section.

By this time, most of the cultivated land had already been parcelled up under the feudal system, so the only land available for endowment to new abbeys was woodland and ‘waste’, including this tract of the Forest of Middlesex. Even before the conquest, however, the abbey had lost some of these lands, and following land swaps, the parish was in secular hands by the 13th century, with the abbey retaining land to the north, over the Hertfordshire boundary.

By this time, Stanmore was divided into two separate strip-shaped parishes according to land ownership: Great Stanmore in the west and Little Stanmore in the east. The Loop proper passes almost entirely through Great Stanmore, though if you choose to split the walk at this point you’ll find yourself in Little Stanmore, as the greater part of Stanmore Country Park and Stanmore station are on the east side of the boundary. Today the divisions have largely been lost to modern patterns of development and the use of station names for wider localities, further obscured by the fact that Great Stanmore was often simply called Stanmore anyway.

The term Little Stanmore is still used for the area southeast of Canons Park station, where the old parish church stood, but the easterly division never had a proper village centre. Great Stanmore, in contrast, did, and by the mid-19th century it was quite substantial, and regarded as picturesque and genteel, spurring the building of ‘gentlemen’s residences’ in the vicinity. The railway didn’t arrive until 1890, when a branch of the London & North Western Railway provided a shuttle service from Harrow & Wealdstone to Stanmore Village, partly at the urging of the hotelier at Bentley Park. But this was too inconvenient for commuting, so building in the area remained largely targeted at the better-off who didn’t need to travel to London on a daily basis.

That changed in 1932 when the Metropolitan Railway opened its branch from Wembley Park to a new Stanmore station to the east. The line provided direct services to the West End and good connections to the city, triggering the intensive development of the southern part of Stanmore over a few short years in the 1930s. The earlier line was eventually closed in 1952, though parts of it can still be traced as footpaths.

As in Harrow, the high, gravelly land to the north of Great Stanmore was managed as common, In the 16th century, part of the common was used as a rabbit warren, with associated earthworks, and much of the remaining woodland was cleared for grazing in the 17th century, creating acid grassland and heath. As grazing declined in the 19th century, birch woodlands established themselves, though there’s now a project to restore some of the heathland.

Although there were some encroachments on the common during the period of inclosure, like Harrow Weald it escaped the development pressures affecting many other parts of London, and the remaining areas were protected as public spaces when the former Hendon Rural District Council bought out the remaining manorial rights in 1929. It’s now a Local Nature Reserve which, like Bentley Priory, is managed by Harrow Nature Conservation Forum. It was part of the same SSSI as the neighbouring site until 1990 when the boundaries were redrawn, and currently doesn’t have SSSI status.

The trail runs a short distance along Warren Lane, its name recalling one of the historic uses of the site, and then cuts through one of the strips of remaining ancient woodland. There’s a substantial area of common to the north here, with a maze-like network of paths and curious earthworks, like the mound known as Foxes Earth, related to the former warren. But the Loop turns its back on these and heads south, crossing Warren Lane again to pass the ground of Stanmore Cricket Club, one of the oldest in the former county. It dates itself from a Court Leet – a meeting of the manorial court in accordance with mediaeval tradition – in 1853, thought to be the last such meeting of its kind in Middlesex, which granted this portion of the common to the club.

Beyond this are the two Brewer’s Ponds, now popular with anglers, but originally created in the late 19th century as a reservoir for the nearby Clutterbuck’s Stanmore Brewery. This was an outgrowth of the brewhouse of the Vine pub at the top of Stanmore Hill, brewing since at least 1749 and closed in 1916. The pub still stands, a little off the route, though after a stint as an Indian restaurant it’s now due to be converted to flats.

Then the Loop runs through an area known as Stanmore Little Common, where the combination of open grass, ponds, hedges, patches of trees and historic buildings provide particularly picturesque surroundings. The two ponds here are the original ‘stony ponds’ that gave the settlement its name, and although they are almost certainly artificial, they’ve been here since at least Roman times. Lower Spring Pond is off the path to the right; a little further is the larger Upper Spring Pond, also known as Caesar’s Pond in acknowledgement of its ancient origin, although of course Caesar himself was never in the area.

The ponds are the break point if you want Stanmore station. The signed link will take you through Stanmore Country Park, created on ancient fields which were farmed until the 1950s, and through the 1930s housing to the station, designed in cottagey suburban style by the Metropolitan Railway architect Charles W Clarke. Curiously, the station has been on three different Underground lines during its history. In 1939 the branch was detached from the Met and became part of the Bakerloo Line, and in 1979 it was reallocated again, as the northerly section of the newly-built Jubilee Line. Despite discussions in the 1930s about a northwards extension, Stanmore remains a terminus. More about the link here.

Continuing on the main route, on the right as you reach the end of Caesar’s Pond is the rambling 18th century Springbok House, formerly Warren House: the mid-19th century yellow brick wall recessed to accommodate a porte cochère was added by an architect who once owned the property. Then a lane leads past a striking modernist house to the gate of the Royal National Orthopaedic Hospital (RNOH), an NHS hospital that’s the biggest orthopaedic specialist in the UK.

The site began as a private house, Verulam House, in 1882, intended for a successful Islington butcher who died before building was completed. It was bought by a trust founded by the philanthropist Mary Wardell as a convalescent home for scarlet fever patients, which opened in 1884 and was substantially extended in 1891 and closed in 1917. The complex became the ‘country branch’ of the RNOH in 1920 and is now its main site. It’s been modified since: the original house has been demolished, so much of what you see dates from the 1891 extension, and there are even some nissen huts installed during World War II that are still in use today.

The London-Hertfordshire boundary running from foreground to background on the edge of Bushey Heath.

Walking between the hospital and the parallel farm drive, you’re once again on an ancient boundary, this time between Great and Little Stanmore. This leads out into fields to a T-junction with another well-defined boundary track, which has divided Hertfordshire, on the north, and Middlesex and then London, on the south, since at least 1595. The Loop leaves London again here, entering a new Hertfordshire district, the Borough of Hertsmere, created in 1974. Appropriately enough, it derives its name not only from the county name but from the archaic word ‘mere’ meaning boundary.

Bushey Heath’s invisible station

The M1 bridge between Bushey Heath and Elstree. The roundabout ahead, where the Watford Bypass (A41) also crosses
the London Loop, was the intended site for the abandoned Bushey Heath station on the Northern Line.

The Loop crosses more fields on the eastern edge of the former parish of Bushey, once another part of the wooded lands granted by Offa to St Albans Abbey. The most prominent landmark today, drawing ever closer on the right, is the embankment carrying the M1 motorway. The trail emerges on the Elstree Road beside a curiously noisy but apparently unattended installation surrounded by a brick wall, actually a gas pumping station. It then crosses two major highways in quick succession, the M1 under a bridge and the A41 across a roundabout, representing two different phases of the transformation of the landscape through road building.

The M1 is the current iteration of one of Britain’s most important highways, from London to northern England and Scotland. The route of this has moved progressively westwards over the centuries, so this is also the first version of it encountered on the Loop. The oldest was Roman Ermine Street, from Bishopsgate via Dalston, Tottenham and Waltham Cross, roughly the route of today’s A10. By the 12th century, due to flooding problems and disputes over bridges across the river Lea, a new route had been created from Aldersgate via Islington, Highgate and Barnet, roughly the route of today’s A1.

These highways inevitably stimulated the growth of settlements along the way, a virtue in the days of horse-drawn and pedestrian traffic, but increasingly a problem as motor traffic grew in the early 20th century. As narrow high streets lined with historic buildings turned into congested bottlenecks, through traffic, once an economic blessing for roadside communities, became an environmental curse. The first solution was to build bypasses, new sections of road avoiding town centres, as well as strategically improving the old turnpikes and coaching routes. For millennia, maintaining roads had been the responsibility of local authorities and, later, toll-charging trusts, but after World War I the creation of a strategic road network became a national concern.

Inevitably, proposals emerged for entirely new roads, optimised for, and legally restricted to, motorised users, with multiple lanes and split level junctions. The first road of this kind, the Long Island Motor Parkway (now long gone), opened in the USA in 1908, and, as is well-known, the fascist governments in Italy and later Germany built substantial networks of such motor roads.

The earliest serious attempt in the UK was an unsuccessful private member’s bill for a motorway between London, Birmingham and Manchester in 1924, followed by detailed proposals put forward by the Institute of Highway Engineers in 1936. The government finally committed to a motorway network in 1946, in the age of radical post-World War II planning. The first UK motorway, which opened in 1958, was actually a short bypass around Preston, now part of the M6. The M1 was the first intercity motorway, with the first stretch opening in 1959, from Junction 5 a little north of here to a junction with the A5 at Crick in Northamptonshire. The section the Loop crosses was added as the first phase of a southward extension in 1966.

The construction of the motorway network was the first nationally coordinated road building programme in Britain since Roman times, and over the 40 years between the late 1950s and the end of the 20th century it had transformed the landscape with the addition of over 3,200 km of new and very wide and obtrusive roads. Not that this solved the problem of congestion: indeed, it seems new roads simply encourage further use of the car and can exacerbate the problem rather than solve it. Bypasses and motorways may have diverted through traffic, but town centres are now clogged with cars making local journeys that would previously have been by walking, cycling or public transport. Yet the association of motor transport with prestige and economic success has been hard to shake.

The road you cross at the roundabout immediately after the flyover dates from the earlier ‘bypass’ period. An old highway through Watford, another strand of the tangle of roads north from London, connected Roman Watling Street (roughly, the modern A5) with Aylesbury in the Chilterns and on to Warwick and the West Midlands. This was identified as a key radial route from London by 1920s planners, with a bypass to relieve Watford town centre as a top priority. By the end of that decade, the lengthy Watford Bypass was taking traffic east of the town between Apex Corner in Edgware to Hunton Bridge. The whole length has been numbered A41 since the 1950s, and between 1959 and 1966 this stretch would also have acted as a feeder route to the M1.

This roundabout has one more story to tell about a transport scheme, this time one that might have been but never was. Had things turned out differently, on the other side of the A41 as you rounded the corner back onto Elstree Road, you’d be walking past a splendid Tube station called Bushey Heath, at one of the extremities of the Northern Line, and on through a whole suburb surrounding it.

In 1935, the London Passenger Transport Board (LPTB), created two years previously to take the capital’s local transport services into public ownership, embarked on its ambitious New Works programme for the Underground. This included a major extension of the Northern Line known as the Northern Heights, largely based on taking over and electrifying several existing local lines then operated by the London and North Eastern Railway (LNER).

The LNER route ran from the East Coast Main Line at Finsbury Park to Highgate and High Barnet, with branches from Highgate to Alexandra Palace and from East Finchley to Edgware via Mill Hill East. The LPTB planned to dig a new tunnel from Archway to connect with the LNER lines north of Highgate, incorporating all three branches into the Tube, and linking at Edgware with the existing Northern Line branch via Hampstead.

It also intended to realise the LNER’s long-held ambition of extending northwards from Edgware to Elstree and Bushey Heath, for which the rights already existed. At the time, open countryside surrounded the northern end of the planned extension, but it was confidently expected that, as with previous extensions, once the Tube arrived, the houses would follow. A major development was envisioned around the station, ringing the roundabout with shops, pubs, restaurants, a bus interchange and even a cinema.

Work on the project was already well-advanced by 1939. The Highgate tunnel was completed, the Edgware branch had been electrified as far as Mill Hill East, and work had begun on the northern extension, including the construction of two intermediate stations and an extensive depot to the east of the Bushey Heath site. But the outbreak of World War II severely disrupted progress. Underground trains ran to High Barnet from 1940, but the rest of the plans were put on hold. The half-completed depot was hastily converted for the war effort into an aircraft factory.

When peace returned, the Northern Heights proposals faltered. Not only were money and resources short, but all the undeveloped land along the northern extension was now designated as part of the Green Belt and unlikely to be built up, so potential passenger numbers were substantially reduced. The proposal was formally dropped in 1954, and the remaining unelectrified sections of the old LNER lines were closed in the rationalisations of the 1960s. Some sections were built on, though substantial stretches of trackbed can be followed on foot today, most notably the section from Finsbury Park to Highgate, now known as the Parkland Walk and forming part of the Capital Ring. The abandonment of the rest of the scheme left the short stretch of line from Finchley Central to Mill Hill East as the anomalous stump it remains today.

Work hadn’t yet started on Bushey Heath station before the war broke out, so today there’s no visible evidence for what was planned here. The roundabout remains surrounded by fields rather than art deco retail units, except for the more recent intrusion of the M1 bridge.

The depot site nearby became a bus overhaul facility known as the Aldenham Works, where 2,500 people worked at its peak. It features in the opening sequence of Cliff Richard’s most famous film Summer Holiday (1962), which was shot during the summer shutdown, using real employees as supporting artists. The complex ceased to be part of London Transport in 1970 when ‘country’ bus services were transferred to the new National Bus Company, and finally closed in 1986. After several years of dereliction, it was demolished and replaced with the Centennial Park Industrial Estate.

Aldenham Reservoir

The unreliable dam at Aldenham Reservoir, originally built by French prisoners of war.

After a rather dull stretch of road past business parks, you round a bend to walk with an expanse of water on the left and a patch of tree-covered wetland on the right. Both are in fact part of Aldenham Reservoir.

Historically this was Aldenham parish, although the village itself is some distance away to the north, and the southern part of the reservoir site now falls within Elstree and Borehamwood. The name means either ‘old homestead’ or ‘Ealda’s homestead’. This was another one of Offa II’s monastic land grants, although for centuries it was disputed between St Albans Abbey and Westminster Abbey. A court case in 1256 resolved the issue essentially by confirming it as under Westminster’s control but with concessions to St Albans. The southern boundary of this land, incidentally, followed the road you’re now walking, Elstree Road: beyond the reservoir, the right hand side, including what became the Aldenham Works, was actually in Middlesex, as part of Stanmore, and joined the London Borough of Harrow in 1964, although it was later taken out of London, as we’ll soon see.

The area to the north of the road became a large common, though most of this had been inclosed by 1801. The fact that a substantial part of it is now covered in water links back to a previous section of the Loop along the Grand Union Canal between Hayes and Harefield. The canal’s developers, the Grand Junction Canal Company, under pressure from mill operators who feared abstraction of water from local rivers, agreed to build their own reservoir to feed the canal, and in 1793 bought 27.5 ha of the former Aldenham Common for the purpose.

French prisoners of war dug the reservoir by hand between 1795 and 1797, building a clay dam across its northern end. But the work was poorly designed and executed, perhaps a reflection on the advisability of using forced labour. The dam had to be repaired, enlarged and strengthened in 1802 when further land was added to the site. In the early 20th century the clay dam was replaced by a concrete structure, but continues to leak, crack and subside to this day.

The site first became a public amenity in the 1920s when the canal company opened it for boating, angling and swimming. In 1938, a consortium of councils bought 38 ha of adjoining land as public space, and agreed with the canal company to preserve the reservoir, now also used for mains water, as a Green Belt amenity. In the late 1960s, Hertfordshire County Council chose the site as the basis for its first Country Park, taking a long term lease on the reservoir from the canal company’s successor, British Waterways. The integrated park opened in 1972.

Unfortunately, Aldenham is now one of the sites on the Loop where the current era of austerity in public funding looms most menacingly. In the early 2010s the council decided the park could no longer be funded, especially as the dam was once again in need of major repair, and threatened it with closure and sale. In 2012, the parkland area was handed over to a private management company, Aldenham Renaissance Ltd, which now runs it on a much more commercial basis than might be expected from the label ‘country park’.

Car parking charges have rocketed and the longstanding rare breeds farm, once free, has become more like a private zoo, with several other paid-for activities like ‘woodlands adventures’, pony and tractor rides and personal appearances by Winnie the Pooh. It’s a vision of the future for our public open spaces which many will find unattractive, though it remains popular with local families on fine weekend days.

The council’s withdrawal from the reservoir has left even more of a mess. The lease was taken on by a development company and has since been sold on to the current leaseholders, Liberty Lake Leisure Ltd, who are proposing a private housing development on green belt land on the other side of the road. This, they promise, will enable them to endow a community interest company that can repair and maintain the lake as a public amenity. The proposals are embroiled in local controversy, with opponents claiming the developers are simply using the lake as a bargaining chip. One planning application has already been rejected; another is under consideration at the time of writing. As you might gather from the notices granting “temporary” permission for the public to use the waterside path, the future of public access is by no means secured.

The trail passes the premises of Aldenham Sailing Club, which has operated here since the lake was first opened up in the 1920s. It then heads off east out of the country park, but it’s worth walking a short distance further along the lake to see the troublesome dam. About halfway along, in the scrub to the north, is a pumping station built in the 1930s to divert some of the water into the mains supply. The other end of the dam is near to the refreshment kiosk, toilets and farm. The area to the left of the drive leaving the park has been designated 100 Aker Wood, where the encounters with Pooh take place.

On the other side of Aldenham Road, the Loop crosses fields that form part of the old manorial estate of Aldenham Park. To the north is Aldenham House, a mansion built around 1672 and extended in 1870, which since 1961 has housed the independent Haberdashers’ Aske’s School for Boys, rooted in one of the mediaeval City of London Livery Companies. The corresponding girls’ school moved nearby on the same estate in 1974.

The British Hollywood

Barbara Windsor commemorated on the Elstree Studio
Heritage Trail. And fling...

Even locals sometimes find it hard to tell the difference between Elstree and Borehamwood. The name of the local station, Elstree & Borehamwood, doesn’t help (it’s actually in the latter). The application of the name Elstree to a much wider area than the original village also reflects the preferences of the area’s most famous local industry, film-making. All but one of the studios that secured the reputation of this leafy suburb on the Hertfordshire-London border as the British Hollywood were in Borehamwood. But clearly the name Elstree tripped better off the tongue than the alternative, which perhaps sounds too like ‘boring’ for a publicist’s comfort.

Elstree is historically the more prominent settlement, though by far the smaller today. It was also part of the Aldenham land grant that St Albans and Westminster abbeys quarrelled over, and in 1188 was confirmed as belonging to St Albans as a separate parish. Its village centre stood at the crossroads of the road to Bushey Heath and Watford (now A411) and Roman Watling Street (A5183) as a typical settlement along a major highway.

Curiously, though, only the northeast quadrant of this settlement was actually in Elstree parish, as both these roads were boundaries. The village ended up spreading across four parishes and two counties: Aldenham, Hertfordshire northwest of the crossing; Stanmore, Middlesex southwest; and Edgware, Middlesex southeast. Although Elstree and Borehamwood Town Council has covered all the northern part of Elstree since it was constituted as Elstree Parish Council in 1894, the anomaly wasn’t resolved completely until surprisingly recently.

When the GLC was created in 1964, it cleaved to the old Middlesex boundary here, so the southern part of the village found itself split between two London boroughs: Harrow west of Watling Street and Barnet east of it. In 1992, following a Boundary Commission review, the London boundary was displaced south along this stretch to follow the M1, placing Elstree entirely within one administrative division for the first time.

Boreham or Barham was originally an outlying hamlet to the east, with its own common and an area of woodland for grazing the abbey’s pigs, which ended up giving its name to the whole settlement. Despite the arrival of the railway in 1868, like its neighbours it remained rural up until World War I. But its good transport links attracted the attention of London-based film producers looking for more space and light and more varied surroundings for location shooting.

The first ‘Elstree’ studio is one of the only two still functioning. It’s the Clarendon Street studio to the north of Borehamwood’s main street, Shenley Road, opened in 1914 by the Neptune Film Company. It passed through several hands, most famously those of Douglas Fairbanks Jr in 1953. He remodelled it to focus on TV production and so it has stayed, used by Lew Grade’s ATV in the 1960s and 1970s and by the BBC since 1984: the latter’s first production there was EastEnders, and the Albert Square set still occupies a backlot.

The studio everyone knows as Elstree Studios was opened by British International Pictures south of Shenley Road in 1927. Between 1969 and 1985 it was owned by EMI, whose original home we passed at Hayes (Hillingdon). When EMI moved out, parts of the site were demolished for a supermarket, but following a local campaign the rest was bought by Hertsmere Council, which still owns it. Among the many famous productions made here are the first British talkie, Alfred Hitchcock’s Blackmail (1927); Stanley Kubick’s The Shining (1980); and the first five Star Wars films.

Gate Studios operated in Station Road between 1928 and 1957, when it became a cinema screen factory. It was demolished to make way for flats, also known as Gate Studios. British and Dominons Imperial Studio in Elstree Way opened in 1930, hosting among others Alexander Korda’s production of The Private Life of Henry VIII, but was burnt down in 1936, though the site was later used by Rank for documentary production, and as a film vault and sound effects library.

MGM British, also on Elstree Way, was built in 1937 but didn’t make its first film until 1944 and closed to be replaced by housing and industrial units in 1970: its most famous production was Kubrick’s 2001: A Space Oddysey (1968). More recently, Millennium Studios operated on Elstree Way between 1993 and 2010 when it moved to Bedfordshire. The only ‘Elstree’ studio not in Borehamwood was the Danziger studios, active between 1956 and 1962. It was actually in Aldenham, on the other side of the reservoir from Elstree village, in a wartime aircraft engine testing shed.

Inevitably the studios drew developers’ attention to the area. A major scheme for a ‘garden’ estate launched in 1937: progress was halted by war, but resumed afterwards in earnest, with both private houses and London County Council estates such as those at South Oxhey swallowing up former farmland. As Borehamwood was closer to the station, most of the development has concentrated there, and it’s become the main shopping and business centre. The stretch of Shenley Road which runs northwest between the station and Elstree Studios has become a bustling postwar high street though, it has to be said, not an especially attractive one.

All this is still some distance away when the Loop deposits you on Watling Street, here known as Elstree Hill. This point is a little to the north of the old village centre, so you’ll need to detour to admire some of the 18th and 19th century buildings and the historic Holly Bush pub, which in part dates back to the 15th century.

The Loop has crossed Watling Street before, at Crayford in section 1. As part of Roman Iter II, it runs from the Channel ports in Kent, through London and on via St Albans to Wroxeter in Shropshire. It later became a coach road and parts were turnpiked in the 18th century. This is another of the important roads from London northwards, which gained an additional importance after the Act of Union between Britain and Ireland in 1800, as it formed a key part of the route between London and Holyhead on the Isle of Anglesey, the main port, then as now, for ferries to Dublin.

Following an Act of Parliament in 1815 which authorised the first centrally-funded civilian road building project in Britain since Roman times, engineer Thomas Telford was tasked with creating a new through route, partly following Watling Street, partly a different alignment via Birmingham. The work culminated in the opening of the famous suspension bridge across the Menai Strait to Anglesey in 1826. The road was identified as one of the key London radial routes in the 1920s and numbered A5. The stretch through Elstree, though, was detrunked when the M1 was opened, and renumbered A5183 in the late 1970s to discourage through traffic.

Junction of London Loop and Watling Chase Trail

On the other side of Watling Street, the trail runs through meadows and then across today’s second golf course, Elstree Golf Club. On the other side is a 16 ha expanse of semi-natural grassland owned by Hertsmere Borough Council, known as Parkfields. This has been managed for centuries as a hay meadow: in the 17th century, its produce was sold at London’s Haymarket. Part of the golf club land is also leased from the council and there’s a long term plan to extend the public space into this. Improvement works in progress will increase tree cover, restore some of the old hedges, encourage wildflowers and return a concrete-lined ditch that runs through the middle to a more natural course.

At a fingerpost on the edge of Parkfields you’ll meet the Watling Chase Trail, opened in the mid-1990s as one of several trails through community forests sponsored by footwear maker Timberland. This starts at Elstree & Borehamwood station and runs north from here through the Community Forest via Radlett and London Colney to Smallford, just outside St Albans, where it links with the London Countryway, a distance of 17 km.

There’s one other small but attractive green space on today’s route, a strip of woodland adjacent to Parkfields and also owned by Hertsmere, known as Allum Lane Spinney. It was originally part of the grounds of a mansion, Boreham House, but has overgrown into thick woodland with numerous mature hornbeam and oak trees. The broad pathway through it was improved recently by Network Rail to replace access for maintenance vehicles and equipment that was lost when a road bridge leading to Parkfields was replaced with a footbridge, and makes a pleasant final stage to the walk.

Into the woodlands of Allum Lane Spinney, Borehamwood.

The Loop then follows the suburban streets of Borehamwood to end this section at the unlikely locale of a mini-roundabout by an Asda petrol station, where the next section heads off south back towards London. Just a few paces further on is a railway bridge with the station immediately on the other side. The station and the line were originally built by the Midland Railway, which began as a regional company serving places like Derby and Nottingham, relying on its competitors to provide connections to London. In 1868 it realised its ambition for a route of its own to the capital by opening this line from Bedford to a new station at St Pancras, still the most spectacular London main line terminal.

Elstree & Borehamwood Station.

No historic buildings remain at the station here, which was ‘modernised’ in 1959 and now has only a dull single-storey building that looks like an overgrown bus shelter. Of much more interest in the forecourt are the murals, Hollywood Walk of Fame-style pavement stars and information panels installed by community group Elstree Screen Heritage as part of a heritage trail. This continues among the undistinguished architecture of Shenley Road, where panels commemorating such luminaries as Dirk Bogarde, Peter Cushing, Peter Sellers and Barbara Windsor might prompt you to ponder how such visionary masterpieces as 2001 could have emanated from such a prosaic-looking place.

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• Official Transport for London page