Site J (1465m², plus three extra trenches 130m = 1595m²), was positioned to provide further context to what, due to its scale, was initially thought to be a quarry, when encountered beneath the foundations of a 19th century garrison prison block in evaluation trench T62. However, the feature turned out to be a late Iron Age to early Roman dyke. Site J was dominated by the discovery of a new part of the late Iron Age Berechurch Dyke (now referred to as the ‘Hyderabad Sector’ of the Berechurch Dyke) that appears to have defined the north-east side of the Camulodunum territorial oppidum. The section of dyke extends the Berechurch Dyke by c.1.0km north of its previously known extent at Colchester Cemetery. Two sections hand excavated through the dyke revealed finds supportive of the conclusion that the ditch was probably a late Iron Age, rather than an early Roman, creation. The ditch then gradually silted up from the early Roman period up to and including the medieval period. An interesting finding is that some of the fill seems to have been dumped from an adjacent occupation site on the southern side of the dyke. This material may imply the abandonment, or deliberate removal, of this settlement, with clearance debris tipped into the adjacent ditch. Inserted into the Roman period central fills was a hoard of 1247 antoniniani, the latest being an antoninianus of Tetricus I, AD 271-4. There were also large foundations of the barracks prison on the site along with service runs, and a number of modern and earlier pits.<1> There were ten pre-late Iron Age prehistoric sherds in the fill of the LIA dyke ditch JF2, a flint flake and a burnt flint. The only sherd which could be more closely-dated was a possible Neolithic Grooved ware sherd from JL04, which is the top fill of ditch JF02. These sherds, while not numerous, demonstrate activity here before the construction of the dyke.