The crypt was originally constructed in the early 8th century. It may have been built as a baptistry, as it was located over a spring.
Later in the 8th century the crypt was converted into a mausoleum for King Æthelbald of Mercia (died 757). Two further burials – King Wiglaf and his grandson Saint Wigstan – were also placed in the crypt.
Excavations by Martin Biddle and Birthe Kjølbye-Biddle in the 1980s showed that the church and the churchyard had formed part of the overwintering site of the Viking Great Army in 873-4.
See also: Church of St. Wystan