Birdlife abounds on the reservoirs of Marsworth and Wilstone.
Distance 4.5 miles (7.2km)
Minimum time 2hrs
Ascent/gradient 70ft (21m)
Level of difficulty Easy
Paths Tow paths, tracks, some fields, 12 stiles
Landscape Gentle clayland of Vale of Aylesbury and four great canal reservoirs, now nature reserves
Suggested map aqua3 OS Explorer 181 Chiltern Hills North
Start/finish SP 919140
Dog friendliness Lots of birds on reservoirs (plus plenty of other dogs)
Parking Startops End Reservoir car park, Marsworth, B489
Public toilets None on route
1 From the Startops Reservoir car park go to the Grand Union Canal, to the left of the Bluebells Tea Room. Turn left on to the tow path and walk under Bridge 132. At the canal junction go left, signed 'Aylesbury 6¼ miles', on to the Aylesbury Arm. This part of the canal was completed in 1814 and is remarkable for its narrow - 7ft (2.1m), locks. Keep on the tow path, passing six locks, until Bridge 2, known locally as Dixon's Gap Bridge. Through the bridge go left over a stile to a footpath alongside a hedge, then along an overgrown green lane into Wilstone village.
2 In Wilstone check out the Half Moon pub and St Cross Church. Pass the war memorial and continue down the main street. Beyond Chapel End Lane and just before the bend go right, through an iron kissing gate and over a stream. Shortly cross a gravel drive, then another footbridge and head diagonally across pasture to a stile. Cross the road, turn left and follow the path alongside the foot of the reservoir embankment. By the Wilstone car park climb steps to the embankment. Turn right, so that the reservoir is to your left.
3 Crossing the bridge at the end of the embankment, the path moves into the tree belt along the west side of the reservoir. Keep straight on across a stream, and climb a stile to cross pasture. This leads to another stile and a footbridge at the head of a reedy inlet. Now in an arable field, the path leaves the reservoir and follows a hedge. It turns left and right to skirt two sides of a field. Ahead is the embankment of the Wendover Arm branch canal. Halfway towards it go left by a footpath post, then right to climb to the canal tow path. Over a stile turn left along the tow path - here the canal is dry and its bed is filled with scrub. Follow the tow path as it winds along the 400ft (122m) contour until it curves sharply right. Here climb a stile, go left to a gate, then turn right on to a lane.
4 Just before some cottages turn left, signposted 'Tringford Pumping Station', along a track. Go left at a signpost (on the right is the pumping station). Over a stile head to a path beneath large horse chestnut trees, to skirt the west side of Tringford Reservoir.
5 Emerging from the trees and scrub, walk along the reservoir embankment to a road. Turn right and at the start of a lay-by car park, cross the road to go sharp left through a kissing gate. This track curves right and emerges from woodland on to the dam between Marsworth Reservoir on your right and Startops End Reservoir to your left. At the canal turn left along the tow path. Where the canal bears right go straight on through a gate into Startops End car park.
Among the many engineering challenges, canal-builders must ensure that enough water is available to replenish their locks many times a day. The Tring Summit of the Grand Junction Canal had many locks up from the south and down into the clay vales to the north, all thirsty for water. The answer was to build reservoirs to store water from local streams and wells, then pump it to the canal as needed. The first was dug in 1802 and is now part of the Wilstone Reservoir. Next came the Marsworth Reservoir in 1806, Tringford in 1816 and Startops End in 1817.
These reservoirs are now nature reserves and are havens for waterfowl and other birds. You can expect to see tufted ducks, pochard, golden eye, goosander, terns, warblers, buntings, water rail, bitterns, cormorantss, great crested grebes and many others. At various points there are bird hides for you to watch this profusion.
The Wendover Arm of the canal opened in 1797, never held water literally or financially - it leaked like a sieve. A stop lock was finally built at Little Tring in 1904 and this stretch became dry.
Wilstone is notorious for Hertfordshire's last witch hunt. A so-called witch, Ruth Osbourn, was murdered here in 1751. After the inquest, held in the Half Moon pub, Thomas Colley, a local chimney-sweep, was hanged at Hertford. Later his body was hung in chains, at nearby Gubblecote.
A mile (1.6km) south east along the canal are the Bulbourne Workshops, now a British Waterways depot. These are a collection of restored brick and slate workshops and stores, mostly from around 1848.
In the evening around Startops and Marsworth Reservoirs you might be lucky enough to see several Brandts bats sweeping through the sky. These rare bats were first recorded here in 1975, their first sighting in Hertfordshire. More likely you will see the commoner Noctule and Daubenton bats hunting insects in the twilight.
At the beginning of the walk at Startops End are two options. The Bluebells Tea Room serves food beyond tea and cakes (accessible from the car park or from the canal tow path south of the bridge). The White Lion (north of the road and opposite the car park entrance) is a typical canalside pub, serving food. In Wilstone village there is the Half Moon pub and a post office and general store.