Denham Spur
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A very short section of road, but not to be mistaken for an insignificant one. The Denham Spur is a short and simple length of road that would have provided a short-cut between other roads - that much is not very controversial.
The reason it is of such interest (and the reason it gets its own page here) is that it raises a number of interesting questions and shines a light into the dark and gloomy recesses of the strategy behind Ringway planning.
A little hint of the intrigue that follows is that the Denham Spur has been filed under 'Ringway 4' on these pages - despite the as-built line of Ringway 4's Western Section having no contact with the Spur at all. It turns out that the Spur might have been instrumental in the planning of Ringway 4.
R4 Western Section & M40
R3 Western Section
The Route
Beginning at the Denham Roundabout, now junction 1 of the M40, the Denham Spur would have connections to the roundabout itself and free-flow links to the M40 west. It would strike north-east from the roundabout, over Harvil Road, and then turning gradually to face slightly more to the north, probably running parallel to Breakspear Road South. It would reach Ringway 3's Western Section just south of Ruislip Common, and terminate there.
History
A small part of the Denham Spur actually exists. When the M40 was extended east to its current terminus at junction 1, the Denham Roundabout, the junction was designed with the Spur in mind. The roundabout there is huge - utterly enormous - leaving space for extra sliproads joining from the spur to the north-east. In fact, there were problems with circulating traffic getting up to inappropriate speeds due to its size and gentle curves, meaning it has since been made two-way and is no longer really a roundabout.
The Denham Spur, with Ringway 4 running to the Denham Roundabout. Click to enlarge
Better yet, the arrangement of west-facing sliproads to the M40 are laid out strangely, and the western motorway bridge over the roundabout incorporates a great deal of extra space to the south of the motorway. There is even a completely disused westbound on-slip to the south of the 'live' one. Unfortunately it's not at all obvious how the junction was supposed to look, but one theory is drawn up on the A40, A40(M) or M40 page.
A former employee with Buckinghamshire County Council tells us that:
"...the big talk in the office then was the NOR (North Orbital Road), which subsequently became the western part of the M25. Remnants of the [Ringways] can be seen as wide verges on the M40 flyover on junction 1 where presumably some slip roads were intended for the Denham spur. It was all hush hush at the time as authority for the Ringway work had not been approved, but the M40 bridge had been designed and built to accommodate it!"
The real interest here (as this page's introduction suggests) is in what this tells us about the rest of the Ringways. Building the Denham Spur would inevitably mean building the Western Section of Ringway 3. Without it, the Spur would end in the middle of a field.
We can't say with any certainty that the Denham Spur was going to be built, of course, because the M40 sliproads and bridge were built without the necessary authority. But it does drop a very heavy hint that the Ministry of Transport's preferred line for Ringway 3's Western Section eventually won the battle of words against the GLC's more urban alignment. If the GLC's urban plan had been preferred, it wouldn't have been worth building in provision for the Denham Spur.
The Spur also presents some useful clues to do with Ringway 4's Western Section. Plans exist showing the section between M40 and M4 terminating at the Denham Roundabout (shown right) - not where it now lies, a few miles to the west. If this were to happen (and the oversized roundabout certainly has a big, inviting gap facing south-west for the motorway to join), the Denham Spur would be the logical continuation of the route for orbital traffic. This is also much more direct than following Ringway 4 all the way around the west of Watford.
This is corroborated by the original line of the North Orbital Road, which was the A412 between Denham and Maple Cross. No evidence has yet been found to suggest where Ringway 4's Western Section was planned between Iver and Maple Cross, so it's perfectly possible that the motorway was meant to travel via Denham.
There it is then, the Denham Spur: a mundane section of road that drops a lot of hints.
