Denham represents perhaps the last outpost of Shire England to the west of London before the capital's sprawl takes over. Appropriately, this circular walk describes a ring around the intersection of the M40 with the M25, but don't let that put you off, as the route provides an excellent way to enjoy a protected area, with remnants of market gardens and nurseries providing a reminder of how the villages around here once supplied fresh fruit and flowers to the capital. Its waterways also provided a means for city dwellers to reconnect with nature, and the walk links with both the River Colne and the Grand Union Canal in its early stages.
At little over 5 miles in total, allow a good two hours to complete the walk. There's a useful Visitors Centre at the start providing refreshments as well as a canalside pub about a third of the way in. Although the path is good most of the way, some sections of fields can get muddy, so boots are recommended, and there are a number of stiles in the latter part of the walk.
The walk starts at the Colne Valley Park Visitors Centre (UP9 5PG), about half a mile north of Junction 1 of the M40, off the A40, which is clearly signposted. Denham is accessible by rail with Chiltern Railways out of Marylebone. Car parking is available, but a charge is made, although for this you do get access to the Centre and its facilities. Picnic tables are also provided here.