Trench XII was located to the east of the North Entrance to the monument, on the site of the former St John’s House. St John’s House was a good example of an early Georgian town house, built in 1734, but it was demolished in 1958 to make way for the excavation of the northern part of the amphitheatre. No architects’ drawings were made of the house, no floor plans survive and the only record made by the archaeologists at whose behest the demolition took place was a series of six black and white photographs of parts of the façade after the roof had been removed. Our best means of gaining information about the house is therefore through excavation.
The most unexpected discovery in the previous season had been that part of the so-called ‘concentric wall’ of the amphitheatre survived to just below the modern ground level. Although the 1960s excavators had concluded that the ‘concentric’ and outer walls had been too extensively robbed in the Middle Ages to justify their excavation and consequently did not seek them, this suggests that they may have reached their conclusion too hastily. The discovery of part of the superstructure of the ‘concentric wall’ allows further analysis of the sequence of building on the site. Since 1960, it has been believed that the stone amphitheatre was preceded by a timber structure, as a timber framework was in place when the sand excavated from the arena was dumped over its foundations. However, it is now possible to demonstrate that so, too, was the ‘concentric wall’; moreover, the concentric wall was faced from the arena side and must have been built before the timber framing. The timbers cannot therefore belong to an earlier building; instead, they represent the support for the front part of the seating, which the 1960s excavators were puzzled by their inability to locate.
The trench that had been dug to remove the masonry of the outer wall was located in 2002, and surprisingly, it cut through seventeenth century deposits. As in Trench XI, this suggests that parts of the building remained visible until well after 1600! Again, no medieval structures were found, reinforcing the suggestion that the late medieval properties known from documentary sources to have occupied this part of the site consisted of alterations to the substantial Roman ruins rather than new build.