In 1972, during salvage excavations to the east of St Giles' Church (in advance of the construction of St Botolphs Circus), a substantial part of a church was uncovered, within the historic St John's Abbey Precinct walls. The church stood on a Roman graveyard, with a large Roman grave directly under the central area. There has been some debate as to the origins of the church, whether it had begun life as a reused Roman Martyrium or mausoleum and whether the church was that referred to by the D. Nero Manuscript <1>, which explains that the Abbey was founded on the site of an Anglo-Saxon church of wooden construction where a priest named Sigeric had a religious house dedicated to St John the Evangelist. For debate see Rodwell <2> and Crummy <3>.

Excavations showed that the church of St John was a three-celled structure, probably of two phases with rubble foundations made with alternating layers of sand and reused Roman rubble. The middle compartment was almost square and this suggests that it had been a central tower. The building had been demolished to foundation level and no floor levels or internal features survived apart from two shallow, sand-filled slots in the west cell. The excavated structure is considered to be Norman in date; no traces of an Anglo-Saxon wooden structure were found. Several medieval graves (including two stone-lined graves) overlay the foundations o fthe church.<4>

The Parish church of St Giles' was founded in the cemetery of the abbey sometime between 1133 and 1171. St John's Church appears to have been demolished by this time. Presumably, the burials that overlay the foundations relate to St Giles'.<4>

The location of the Church has been plotted based on Crummy 1991, Fig. 37; only the N. half was exposed and the S. half is, therefore, projected.<4>