Archaeological recording and monitoring. Monitoring during Water Lane underground services works. Three foundations were observed which were elements of the basin that originally existed to the rear of St Thomas's Tower. Two of the foundations- made respectively of chalk, siltstone and hard limestone blocks and blocks of chalk and Reigate- were medieval (possibly c. late 13th century). The third foundation comprised ashlar blocks and was a later addition.
Derek Gadd (Wed,) studied this question.