A poorly understood ENE-WSW dyke with northern and southern ditch linking with Shrub End Dyke and Lexden Dyke Middle (Bluebottle Grove). It is undated but conjectured to be a Roman structure built during the invasion year. The fact that it has a ditch on both sides suggests that it was reversed at some stage.

In 1936 Rex Hull excavated the so called 'Peartree Junction'. Hull sectioned the Dyke at the beginning of its ENE course at Shrub End, revealing the rampart and a filled in ditch either side of it. The rampart had been lowered, but enough remained to show that it had been faced with turfs on the north side. The northern ditch was slightly larger than the southern one (the later being 3.7m wide and 1.2m deep). Hull deduced that the northern ditch was the primary one. A ditch was placed across Shrub End Dyke ditch and Hull found that the Prettygate dyke appeared to be built across both the rampart and the western ditch of Shrub End Dyke. Prettygate's northern ditch did not cross the rampart, but the southern one did, tapering north slightly as it crossed the Shrub End rampart then turning to run onto its western ditch.

Hull was looking for evidence of a Roman road on the Prettygate Dyke but found no agger. He looked to see if the rampart had continued across the Shrub End ditch and found that it had a partial filling capped with gravel metalling at this point. When this possible causeway was made the ditch had already silted up 45cm. Unfortunately half of the dykes potential course was quarried away in an old gravel pit (MCC8177).<1><2>

An unsigned written report detailing observations made during service trenching around Prettygate in June 1947 and May 1947 is held in the Museum Resource Centre in the General Information Files (Dykes Project Source File 21). Field numbers are given relating to the 1936? OS Map with approximate measurements given in paces and feet. It appears that Prettygate Dyke was sectioned in places. No finds were recovered.

A number of trenches were dug at Prettygate Junction by C.F.C. Hawkes in 1956. The dyke’s northern ditch was found to end joining the ditch along Bluebottle Grove. The junction of the rampart fell below a footpath and was not examined. Hawkes believed that the dyke post dates Shrub End and Bluebottle Grove and that it was built before the Roman conquest. After the conquest he suggests that it was reversed by the filling in of its northern trench and the digging of the southern one. This was undertaken, he suggests, to protect Legionaries camped behind the newly fortified Triple Dyke. Later in the Roman period he suggests that it was slighted for use as a Roman Road which passed through the junction between Bluebottle Grove and Lexden Dyke South. Excavations east of the Junction revealed the line of Prettygate southern ditch curving south with a smaller NE-SW ditch where the rampart should have been if it had continued. Excavations were halted by a Prettygate farmer 'bearing down on us on the spot'.<3>

A watching brief was held along King Harold Road in 1977 during the installation of a new sewerage system (MCC8058). The contractor’s trench had cut through Prettygate Dyke. The profiles of two late ditches were recorded by Dennis Gamble (Colchester Borough Council engineer).<4>