In addition to the triple chancel arch, the apse also indicated a close relationship with the Kentish group. The apse was not popular in England, although it was a characteristic of the Kentish group. The apse was originally semi-circular, but was later modified into a polygonal shape on the outside. The crypt ambulatory dates from the original apse but is usually assigned a late eighth or early ninth century because, with the exception of Brixworth, this style of ambulatory was not known until that period. Brixworth has a subterranean ambulatory of a non-existent crypt under the sanctuary.
Crypts are rare in Saxon churches and suggests an Italian or a Carolingian influence.
The purpose of the ambulatory is not clear. It may have been used to house relics and the walkway would have provided access for the pilgrims. There is relic that is said to have come from the body of the eighth century Anglo-Saxon missionary, Boniface. It has been suggested that the crypt was built to house this particular relic. An alternative suggestion has been made recently, and that is that the crypt may have been designed for burial use.