Thetford, the major market town of South-western Norfolk, consists of three ancient parishes. Technically St Mary's parish was largely within Suffolk and indeed the church itself, south of the river, was in Suffolk until boundary changes in 1974. Thetford was the ancient capital of East Anglia long before the cities of Norwich and Ipswich grew to prominence, the town sits on the ancient A11 trunk route and was always a major market for the surrounding area.

St Mary's church is nor no longer used for services and looks a little sad within its churchyard. Parts of the church indicate 11th and 12th century origins and the squat looking tower is probably 15th century but there was a major restoration and rebuild in 1850 which serves to mask many of the original features.