St Mary's has an aisled nave with a clerestorey. The nave is more or less rectangular in plan, but the arcades to N and S are differently treated. On the S are five uneven bays; the two western bays round-headed and the remainder pointed. The N arcade piers are more regularly spaced, i.e they are entirely out of step with those on the S. In the N there are three round-headed bays at the W end, then two full-sized pointed bays and a short pointed bay, leading to a vestry and partly blocked with a later doorway inserted. These different arrangements bring the two arcades to roughly the same point, and here the aisleless chancel starts, although there is no masonry chancel arch. The liturgical arrangements have been altered at some time, and a chancel step built right across the nave at S pier 1, which is part-way along the first full-sized bay on the north. This bay now houses the organ, and the liturgical changes have brought it into the chancel. The chancel is short and square-ended, substantially 13thc., although on its E wall are the remains of an earlier round-headed window. The W tower arch is 12thc., but a pointed arch has been inserted to reduce its size. The tower itself has a tall lower storey of rubble with plain 12thc. windows, and to which a 13thc. storey has been added. There are N and S nave doorways, both under 19thc. porches. Romanesque work is found in the nave arcades, the tower arch, the N nave doorway and a piscina set in the S nave aisle. The church was restored by Ewan Christian in 1885-87 (N and S porches, N aisle wall), and by H. F. Traylen and F. J. Lenton in 1933-35 (tower).