The archaeological work on site consisted of three separate interventions: an excavation in the area of the grout box, a targeted watching brief on the area of the Main box, and a general watching brief during ground reduction of the rest of the site. The excavation of the grout shaft area was done in two phases in order to get a full east-west section across the shaft. The intention of this excavation was to explore the results seen in the evaluation that uncovered the eastern edge of the main channel of the Walbrook. During this phase the channel was successfully recorded across the width of the trench. Natural sand and gravels were seen at the base (5.90m OD) followed by a succession of flood deposits, marshy peat, and a Roman dump layer which contained a number of pieces of pottery and ceramic building material dating between 50 and 400 AD. The targeted watching brief in the southern portion of the site recorded a probable continuation of the Walbrook Channel with Roman dumping layers and a north-south running ditch. In the south-east corner of the site the targeted watching brief recorded natural terrace gravels at a much higher level (8.33m OD) than in the grout shaft, suggesting this would have been dryer ground near the edge of the Walbrook. An east-west running ditch cut into the subsoil and underlying natural terrace gravels dated to the 12th century by pottery found within the fills. This was in turn cut by a north-south running ditch. These may represent medieval attempts to drain the higher ground to the east into the Walbrook. The general watching brief on ground reduction across the rest of the site revealed late 19th/early 20th century brickwork and rail ines in the northern portion of the site, probably related to Metropolitan Line.
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