A gatehouse guarded the entrance to the Castle Bailey, situated in the south-west corner of the Upper Bailey (Museum Street). Sometimes referred to as the 'Dunbarr Gate'.

The gate appears to be shown on Speed's Map of 1610.<1> The name 'Dunbarr gate' appears on a (now lost) manuscript dating to c.1709. A photograph of the original is reproduced in Drury's article on Colchester Castle; it is also reproduced as Fig. 6 in CAT Report 521.<3><5>

A series of extensive medieval foundations, c.0.3m bgl, were defined below Museum Street during re-surfacing work in 1986. These probably formed part of the gate and an outer barbican at the main entrance into the Upper Bailey. However, these proved difficult to interpret as they were only partially excavated, due to the time and depth restrictions, and they were not all exposed at the same time. They were also much disturbed by later features, especially modern service trenches. There was also little direct dating evidence.<5>

The foundations were of broadly similar construction, which differed from that of the Roman foundation. They consisted of a yellowish sandy mortar occasionally with visible shell inclusions. They incorporated fragments of re-used Roman brick/tile, septaria, and occasionally greensand, often with Roman mortar adhering to them. There was a conspicuous absence of post-Roman brick, peg-tile and slate. They were often associated with loose amorphous spreads of mortar and rubble. The lack of clearly-defined ground surfaces contemporary with the foundations meant that it was unclear how far, if at all, they originally projected above ground level. There was little direct dating evidence for any of these foundations.

Additional observations relating to these foundations were made during a watching brief at 3-7 Museum Street in 2010.<5>

A piece of masonry possibly belonging to the gate was excavated in 1986 (MCC2073).<2>

Discussion of the origins of the name 'Dunbarr' Gate by the late local historian, James Fawn, provides links to several individuals who have occupied the area in the 17th-18th century. <4>