The Devil's Dyke is a massive bank and ditch lying in Cambridgeshire. Carbon 14 dating indicates it was built in the 6th or 7th century AD and, given the ditch is to the south east of the bank, this would suggest it was built by the East Anglians to protect against their British neighbours.
Over 7½ miles (12km) long, it stretches from the village of Reach to the village of Woodditton. Reach lay at the edge of the fen and from Woodditton the country was heavily wooded. The dyke therefore covered a vulnerable point in a much longer border. It is the largest and best preserved of four linear earthworks in the area, all running roughly parallel. Three Roman roads cross the dyke, including the Ickneild Way (now the A1304/A11).
It is unlikely that such linear earthworks were ever manned except at the crossing points. Their function would have been to act a trip-wires so that enemy incursions could be quickly identified and a mobile force sent to intercept them, and to prevent raiders from escaping with any but the most portable goods since they would have been difficult to cross with horses laden with goods or with livestock.
See also:
Devil's Dyke at Gallows Hill
