A large defensive ditch dating from the early 2nd century AD to the end of the Roman period.

At the Balkerne Lane excavations (ECC332) the ditch was examined at a number of points and recorded as being about 15m wide and 3.75m deep although it was impossible to determine its original dimensions and profile. The ditch was designed to work in conjunction with the defensive wall of the Roman colonia (MCC859).

The plan of the ditch in its final form suggests that it underwent several phases of enlargement including a substantial widening during the 3rd century. During the 4th century a new section of ditch was dug across the main Colchester to London street (MCC475) in order to join the two butt ends of the town ditch together. The lack of evidence for a bridge suggests that the Balkerne Gate (MCC555) then went out of use.

From the end of the Roman period to late Anglo-Saxon times the ditch gradually silted up with an accumulation of topsoil and small-scale dumping.<1>

At Culver Street observations of the ditch were limited to a contractor's service trench but as far as could be judged the ditch was about 4.5m deep, 20m wide and filled with dark earth. There did not seem to have been a berm between the wall (MON570) and the northern edge of the ditch. There were also indications that the ditch had been preceded by an earlier ditch which may have been a continuation of the Flavian period ditch at Balkerne Lane (MCC539).

Observations of the town ditch were also made during the laying of a new sewer pipe in Castle Park (see ECC375). The ditch was 16m wide with the inner edge being about 10m north of the town wall. A layer of sand 0.3m deep sealed the natural sandy clay loam in places and may represent the base of a counterscarp bank as noted elsewhere.<2>

The centre-line of a large ditch was clipped by the south-west corner of an excavation trench dug ahead of the creation of a new subway for the Inner Relief Road at Crouch Street in 1973 (ECC398). It appeared to be the southern end of Roman town ditch at Balkerne Lane. Its original level could not be determined but its base was 3.7m below the modern street level.<3>

A watching brief was held during groundwork for the construction of a disabled toilets extension to the public convenience block in Castle Park. The extension to the north side of the block involved excavation of 0.7m wide wall trenches to a depth of 1m. The lowest 0.25m of the trench contained a very dark soil which may represent the fill of the town ditch. This was sealed by a 0.55m deep deposit of sandy loam overlain by modern asphalt.<4>

A watching brief was held during the construction of a two-storey building at the rear of 37-8 St John's Street. The northern frontage of the new building was built over the remains of the Roman town wall. This was damaged during construction work when it was partly undermined by a trench dug too near to it. The exposed section of the wall appeared to be only core (on the south side).<5>

Excavations were undertaken by members of the Colchester Archaeological Group (EVT3083) under the auspices of the Colchester Excavation Committee and directed by P.R. Holbert. The object of the excavation was to recover details of the town ditch. On completion of work on the inner lip of the ditch, a small section of masonry belonging to Bastion No.3 was identified and included in the investigation. Mechanical excavation on the ditch consisted of a trench 40ft long and 10ft wide at a distance of 2ft from the western wall. The base of the excavated ditch was waterlogged. Work on the bastion was concentrated on the most important features of the eastern half and the point where the western end joins the Roman wall.<6>

In 1913, excavations to repair the town drains revealed a number of interesting features along Head Street and St John's Street. The trench revealed part of the town ditch, various burials and other finds were recorded For a full account of the other discoveries please refer to <7>. For a detailed review of this article see Hull's notes.<8>

A watching brief was held during construction of the eastern subway of the Inner Relief Road built in 1973. (See also ECC398). Two ditches were observed the upper of which may be the Roman Town ditch (AD 250-400) identified at Balkerne Hill.<9>

A watching brief was held during the construction of a rear extension in the back yard of 42 St John's Street. Building work revealed a section of the town wall and excavation of two trenches led to the discovery of quantities of medieval and post-medieval pottery. One trench sited by the rear door was dug to a depth of 2m below ground level revealing black topsoil which "was presumably the north edge of the town ditch". A lens of burnt clay or daub was noted at 1.2m depth.<10>

In 1935 the outer lip of the Town ditch was cut away in the laying out of the Park bowling green. Great quantities of pottery and other Roman objects were found, but the most striking discovery was that the upper 3ft of earth (all that was moved) was full of disturbed human bones. It was as if the ditch had been enlarged after it had been used as part of a cemetery for a great number of inhumations (The burials were considered by Hull to be possibly Anglo-Saxon).<11><12>