Grade I listed building. Main construction periods 1100 to 1199. A 12th century stair case which originally lead to the mid-12th century first floor hall known on a contemporary plan as the "Aula Nova" possibly part of the almonry of the priory. Excavations within the vicinity of the staircase were carried out in 1978-9. The most important structural remains that were found date from the mid 12th century and consist of the east wall of the vaulted undercroft of the hall and the monastic drain which led from the 'necessarium' on the south side of the Green Court to the northern city ditch. The mid 12th century building levels completely sealed Late Saxon and Early Norman levels. A pit and a small lane which must have led off the intra-mural street nearby were also found.