The building of churches in Anglo-Saxon England essentially began with Augustine of Canterbury in Kent following 597; for this he probably imported workmen from Frankish Gaul. The cathedral and abbey in Canterbury, together with churches in Kent at Minster in Sheppey (c.664) and Reculver (669), and in Essex at the Chapel of St Peter-on-the-Wall at Bradwell-on-Sea, define the earliest type in southeast England. A simple nave without aisles provided the setting for the main altar; east of this a chancel arch separated the apse for use by the clergy. Flanking the apse and east end of the nave were side chambers serving as sacristies; further porticus might continue along the nave to provide for burials and other purposes. In Northumbria the early development of Christianity was influenced by the Irish mission, important churches being built in timber. Masonry churches became prominent from the late 7th century with the foundations of Wilfrid at Ripon and Hexham, and of Benedict Biscop at Monkwearmouth-Jarrow. These buildings had long naves and small rectangular chancels; porticus sometimes surrounded the naves. Elaborate crypts are a feature of Wilfrid's buildings. The best preserved early Northumbrian church is Escomb Church.