A trial-trenched evaluation was carried out by Colchester Archaeological Trust on a 0.2ha site at Colnebank House, 30 St Peter's Street, Colchester, prior to redevelopment. Historic map regression indicates that the site remained undeveloped in the post-medieval period, and remained so until 1826 when a silk mill was constructed by Stephen Brown & Co. The mill buildings were demolished in 1967, and Colnebank House was built by the Royal Mail.<1> This evaluation was followed with the excavation of three test pits inside the building 2013. <2> Four trenches were excavated around Colebank House. T1 was positioned to the north of Colnebank House, and was the nearest trench to the River Colne. It was excavated through three superimposed layers: L1, a rough layer of poorly-consolidated,100-150mm-thick tarmac hard-standing; L2, gravel and crushed brick hardcore approximately 250mm thick; and L3, a 1.5m-thick layer of alluvial silts which contained residual Roman brick and tile, and shell fragments. L3 sealed the natural yellow/orange coarse river gravels (L4), the top of which was between 2.5m and 2.7m below ground-level. The trench revealed three modern foundations (collectively numbered F4). From the 1876 OS map showing the ground-plan of the mill, it would appear that foundation F4 was part of an ancillary building, perhaps the ‘smithy’. T2 was located between Colnebank House and its boundary with the former CBC depot (on the east side of Colnebank House). It was excavated through three superimposed layers: L1, a rough layer of poorly-consolidated,100-150mm-thick tarmac hard-standing; L2, gravel and crushed brick hardcore approximately 250mm thick; and L3, a 1.5m-thick layer of alluvial silts which contained residual Roman brick and tile, and shell fragments. L3 sealed the natural yellow/orange coarse river gravels (L4), the top of which was between 2.5m and 2.7m below ground-level. The water table was also at this level (ie the top of L4). The only feature in this trench was a modern concrete slab (F5). The plan of the mill on the 1876 OS map suggests that F5 was part of the foundations of an ancillary building. Alternatively, the slab may be of more recent origin, possibly part of a raft foundation belonging to Colnebank House. At the southern end of the trench, the concrete slab was broken through, revealing a layer of crushed hardcore which sealed the alluvial silts (L3) seen in T1. T3 was located in the south-eastern corner of the site, along the north side of the boundary with St Peter’s Street. It was excavated through three superimposed layers: L1, a rough layer of poorly-consolidated,100-150mm-thick tarmac hard-standing; and L2, gravel and crushed brick hardcore approximately 250mm thick. L2 sealed a concrete slab foundation (F6). The plan of the mill on the 1876 OS map suggests that F6 belonged to an unnamed building associated with the mill (a ?warehouse). It is also possible that the slab was of more recent origin, perhaps part of a raft foundation belonging to Colnebank House. Unlike the concrete slab in T2, F6 was intact along the whole length of T3. This means that its thickness and the nature of any underlying strata could not be established. T4 was located in the south-western corner of the site, along the north side of the boundary with St Peter’s Street. It was excavated through three superimposed layers: L1, a rough layer of poorly-consolidated,100-150mm-thick tarmac hard-standing; L2, gravel and crushed brick hardcore approximately 250mm thick; and L3, a 1.5m-thick layer of alluvial silts which contained residual Roman brick and tile, and shell fragments. L3 sealed the natural yellow/orange coarse river gravels (L4), the top of which was between 2.5m and 2.7m below ground-level. The water table was also at this level (ie the top of L4). T4 contained three modern features: a brick foundation (F1); a highly-compacted gravel surface (F2); and a concrete stanchion (F3). Brick foundation F1 extended along the whole length of the trench on its northern side. The plan of the mill on the 1876 OS map indicates that F1 had been part of the mill’s office building. Similarly, surface F2 appears to correspond with the yard area surrounding the mill. F3 was a modern stanchion almost certainly associated with Colnebank House.