Sheepen Dyke protected the Late Iron Age settlement on Sheepen Hill along its western edge. The dyke ran from near the Colne River over Sheepen Hill to the south, to meet a tributary stream of the Colne on the south side of Sheepen Hill. A further leg was added to the dyke to extend the protected area also in the Late pre-Roman Iron Age.

The remains of the dyke ditch (Ditch I) were extensively investigated during the excavations at Sheepen undertaken by Christopher Hawkes and Rex Hull, 1930-39, when 30 sections were excavated across it. The excavations proved the NNE to SSW course (i.e. facing NW) of the dyke ditch (depth of up to 3m and c.9.1m wide) for c.530m, before turning a near right angle and forming a corner (with a SW entrance) and traced for a further c.270m NW to SE (Ditch IB), i.e. the whole being L-shaped in plan.

A further stretch of ditch, 340m long, was defined from the SW corner, aligned NE to SW (Ditch IA).

The work also defined traces of the demolished rampart (thought to be proportionate to the ditch), which left traces in two places on the east side of the ditch. The dyke was clearly a defensive work which was originally V-shaped in plan with sides roughly 700 and 280m long (the two legs).

A date of c.AD 10 is suggested for the construction of the dyke (Sheepen Period 1), and it is believed to have been levelled after the Roman conquest.<1><2>

Ditch IA of the Dyke was traced during the construction of Endsleigh Court Road to the west of Sussex Road in 1959 (ECC2306).<3>