It's the motorway junction of the year, it's J20 M25. (If the M20 had 25 junctions yes, that would be better, but it only has 13 so we're off to Hertfordshire instead)
J20 is the northwesternmost junction on the M25, an interchange with the A41 and the designated exit for Hemel Hempstead and Aylesbury. It's on the outskirts of Kings Langley, one stop north of Watford Junction. Unlike J19 and J21 you can actually walk round it, which is fortunate for blogging purposes. And I should probably start by explaining how it came to be where it is.
After WW2 there were plans to build a series of four concentric Ringways to motorway standard to carry traffic around London. The inner Ringways proved exceptionally controversial due to the amount of demolition required so were swiftly dropped in 1973 when Labour took control of the GLC. The focus then switched to the outer Ringways which were to be combined to create a single London orbital following the line of least resistance, essentially combining the route of Ringway 3 to the north and east with the route of Ringway 4 to the south and west. This left an unexpected gap in the Watford area so in November 1974 a consultation was put forward offering several possible routes to connect Micklefield Green (Ringway 4) to South Mimms (Ringway 3).
With great foresight I acquired a copy of that consultation document 50 years ago and retained it, so here's the fold-out map at the back :)
Three options were proposed for the western route, each bearing off from the North Orbital Road at a different point. This was already under construction and would be completed in 1976, ten years before the fresh link round the top of Watford. Route 1 diverged early near Sarratt and cut across fields to cross the Gade Valley between Kings Langley and Abbots Langley. Route 2 bore off later and passed west of Langleybury to join route 1 before crossing the valley. Route 3 followed the full length of the new road to Hunton Bridge but would then have required building a tunnel underneath Leavesden Aerodrome, this long before it was a famous film studios. All three routes were designed to interchange with the new A41(M), a bypass which ultimately opened in 1993 without achieving motorway status.
Route 3 was the shortest (2.1 miles) and also the least damaging to 'distinguished landscape', but also by far the most expensive (£15m) because of the tunnelling. Route 1 was the longest (4.5 miles) and the most environmentally damaging, though it did require demolition of the fewest number of dwellings. At 3.7 miles long Route 2 proved the happy medium and was also the cheapest of the three options with costs estimated at £6.1m at November 1974 prices. Route 2 was thus duly chosen and duly built, opening in October 1986, and I imagine taxpayers carped and criticised the eyewatering costs (Six Million Pounds!) even then. Selecting route 2 also meant that junction 20 ended up on the edge of North Grove Wood in fields beside the existing A41 Watford Road, and that's how it came to be where it is.
J20 M25 is essentially a big five-armed roundabout with the M25 swooshing across the top. Two of the arms are thus motorway slip roads, two are the new-ish A41 dual carriageway and the other is the A4251, which is what the A41 used to be. One side is in the district of Dacorum and the other in Three Rivers because the planners chose to build it straddling the boundary. Also one side has traffic lights and the other doesn't. As a pedestrian this makes crossing the M25's anti-clockwise off-slip dead easy but crossing the on-slip potentially deadly, so although it's perfectly possible to follow pavements across the junction it isn't necessarily wise. This hazard mainly bothers residents of North Grove Cottages, two properties left narrowly unscathed when the motorway was built but which now find themselves adrift on a brief dead-end spur on the alignment of the original main road.
The M25 is elevated here because it's about to cross the Gade Valley Viaduct, a significant structure which carries the motorway across the Grand Union Canal and the West Coast Main Line. Technically it's a 450m-long box girder bridge comprising twin decks, both fashioned from four open top steel girders with an in-situ cast concrete slab. Aesthetically it's very elegant, as is easily seen from a passing train, although for three years recently it needed a cage of scaffolding underneath because the welding of the structure's bottom flange needed urgent reinforcement. Thankfully all that's cleared, so I got the best view by walking the canal towpath underneath on a bright sunny day - sweeping curves, thin trapezoid pillars, crystal clear reflections - all just before a narrowboat chugged through and rippled the lot.
The first field to the north appears empty, and the 'Bull in field' sign on the gate looks entirely unconvincing. But this grass pasture is actually a scheduled monument, the site of a medieval royal hunting lodge called Little London, and what's more several traces survive. Chief of these is a rectangular moat surrounding an island 120m long and 60m wide with a causeway on the western side. The moat's dry these days and the eastern side has been filled in, but the remainder is a dry channel approximately 12m wide and 1.5m deep with further low earthworks outside which may be the remains of ancillary buildings. It's very hard to distinguish any of this from outside the field so the layout is best imagined from above. And it turns out the lodge is here because, a tad to the north, Kings Langley used to be the site of a significant royal palace.
Queen Eleanor of Castile acquired the hilltop site in 1276 and started building works, with the palace passing to her son Edward II in 1302. During the Black Death Edward III used Langley as his seat of government, it being safely out of the way, and his fourth son Edmund de Langley was born here in 1341. Edmund is crucial to Plantagenet history because he was the first Duke of York and the founder of the House of York, one of the two sides in the internecine Wars of the Roses. Edmund's nephew Richard II loved Langley Regis so much that he spent Christmas here twice, and after being deposed was initially buried here before being shifted to Westminster Abbey. Shakespeare even set Act 3, Scene 4 of his play Richard II here, although it's hardly a classic.
SCENE IV. LANGLEY. The DUKE OF YORK's garden. Enter the QUEEN and two Ladies
QUEEN: What sport shall we devise here in this garden,
To drive away the heavy thought of care?
Lady: Madam, we'll play at bowls.
The palace fell into decay during the Tudor period and the priory on site was inevitably trashed by Henry VIII. In the 20th century the site was used for a large boarding school, most recently a Rudolf Steiner School, which further destroyed the overall footprint so excavations in the 1970s didn't find much. The best place to be dazzled by Kings Langley's royal connections is thus the parish church of All Saints, a fine flint building dating back to the 13th century. Its Royal Chapel contains the marble tomb of the aforementioned Edmund de Langley, 1st Duke of York, which is decorated with painted shields and has been here since the Priory was dissolved. An information panel references the suspicion that the tomb is so ornate it was probably meant for Richard II, and mentions that the stained glass window immediately above was donated by Queen Victoria. It's quite a thought that the bones inside are of a man whose lineage directly ruptured English history, and here he lies in a building that hosts Tiny Tots and a foodbank every Tuesday.
Before I leave Kings Langley I should of course mention the Ovaltine factory, opened on Station Road in 1913 and greatly expanded during the 1920s as the nation's love of hot malted drinks increased. Across the road were established the Ovaltine Model Dairy and Model Poultry Farms, top-class facilities which helped provide the drink's main ingredients and which also inspired the dairymaid logo which appeared on later packaging. The factory is of course now luxury flats and has been since 2006, with addresses on Ovaltine Drive and a flurry of Private Property signs to keep other villagers at bay. As for the farms they proved so attractive to the M25's civil engineers that they built the motorway straight through them, this particular option being known as the 'egg farm route'... and hey presto we're back at J20 M25, the motorway junction of the year.
