An archaeological watching brief was undertaken at Cromford Canal during June and July 2024 and June 2025. The purpose of the watching brief was to record any archaeological remains that survived on the site during construction works for a flood storage compensation channel, part of the flood storage compensation scheme for the River Erewash required to be constructed as part of the development prior to commencement of restoration of the Cromford Canal channel itself. During the watching brief an area c. 112m in length and up to 10m wide was investigated, which partially covered the route of the earlier canal and lock structure of Marshall’s Lock at Langley Mill. The sides of the watching brief flood storage channel were battered at a c.45°angle resulting in a 45m width exposed along the watching brief area at the gully excavated design depth. This location was mostly within the former Cromford Canal, which had been built by 1793/4. The watching brief area was machined under archaeological supervision to between 1.6m and a maximum depth of c. 2m below present ground level. A depth of c. 1.5m was required for the redevelopment of the site. Only a single archaeological feature was identified, located at the southeastern end of the flood storage channel, of a joined structure over of c. 12.75m in length orientated north-west to southeast. Historic maps showed that this area of brick and stonework had been part of the former Marshall’s Lock and the remains align with the northern part of the western lock wall and part of the northern lock gate foundations. This structure predominantly comprised brickwork but with one internal place of stonework recovered, and two square buttresses abutting this brick and stone area on its western side, which presumably collectively was for strengthening. This lock gate would have had a complex and weighty mechanism on the ground surface which needed supporting below. This brick and stonework survived as a very truncated set of features, with no more than three courses recorded (though there were further courses, at least in parts, below where excavated level). The walls were found at c.60m aOD, with the ground level at this location being c. 61.6m aOD. The other parts of Marshall’s Lock and the brick walls of Cromford Canal in this area at this excavated level within the watching brief had presumably been machined removed in the 1970s/1980s without archaeological recording before this area had been backfilled with rubble. It is worth noting that the lowest deposit exposed across the watching brief (apart from the structure) was extensive at up to more than 1m deep and importantly it contained c. 20% brick fragments. No artefacts were collected from the watching brief.