Alton Barnes is a village 6 miles E of Devizes in Wiltshire. The church of St Mary has Anglo‑Saxon origins, and retains long‑and‑short work at the west end of the church. it consists of nave and chancel only, with a west window and north doorway added in the C14th and a new roof in the C15th. The nave was decorated with external pilaster strips. The chancel was rebuilt in brick in 1748 but excavations revealed the existence of an earlier chancel. Alterations and restorations occurred in 1832, 1875 and 1904.

The only fabric which may be Romanesque is the blocked north door and the impost of the chancel arch. The chancel arch is said by Pevsner to have been rebuilt in 1832.

A settlement at Alton Barnes is mentioned in DB, but not a church. According to the VCH, the king allowed Henry of Cerne to exercise the advowson in 1216. The church was valued at £5 in the 1291 Taxatio.

The chancel was rebuilt in brick in 1748 and according to Pevsner the chancel arch was taken down in 1832. Its character seems to bear this statement out, but the impost blocks of the arch appear to be earlier than the arch. In Pevsner they are described as Anglo‑Saxon, but their form, with a roll‑moulded upper member, appears to be post‑Conquest.