In 1940, during World War II, the clearance after destruction caused by bombing revealed an archway built of reused Roman tiles and stonework, set in a surviving wall of the medieval church. The reuse of Roman building materials, and comparison with arches in the early Anglo-Saxon church at Brixworth, Northamptonshire, suggested that the All Hallows arch was very early in date, and that an original church could have been built as early as the 7th century. This seemed to confirm the belief that the church had been founded as a daughter church of Barking Abbey at about the same time as the abbey itself was established, although it is doubtful that the first construction on the site would have been in stone. It is more likely that the stone church, of which the arch is a remnant, superseded an earlier wooden building. Recent research, and archaeological evidence that Roman tiles and stone were being used in the construction of other London churches as late as the 11th century, suggest that the arch could have been constructed at any time between the 7th century and the arrival of the Normans. Fragments of three 11th-century stone crosses also found during archeological work in the 1930s and clearance works after the bombing, now displayed in the crypt, also date from this first church.