An archaeological watching brief was carried out along the road line of East Stockwell Street, Colchester during trenching for the replacement of the gas main. 17 trenches of variable sizes and depths were dug by contractors between the High Street and Stockwell to expose the joins of the existing gas main. A new pipe was then inserted into the existing pipe and pushed through. The width of the trenches varied from 380mm to 900mm and the lengths were between 900mm and 7.9m. The trenches were dug to between 500mm and 1.35m deep. Intermittent monitoring visits were made. The ground had been disturbed by the existing gas main and other services. However, near William’s Walk (T1), a wide robber trench was recorded extending east to west and filled by Roman building material. This robber trench had been dug to remove a wall foundation of a large Roman building. In one of the northernmost trenches (T18), two mortar layers appear to represent floor bases from two phases of a Roman building. <1>