This church has a very important 12th century east end, and probably originally had an aisleless 12th century nave which was replaced in the 15th century. The east end consists of a two bay, vaulted chancel with small transepts and a tall tower which is rectangular in plan. The openings on the central tower were altered in the 15th century. In the 15th century the Lamb Chapel was added to the north side of the chancel and the larger Beauchamp Chapel to the south. The western bay of the nave and the west façade was replaced in 1863 by Slater. Some of the stones of the former west door were apparently reused in the grounds of the castle.

Romanesque sculpture survives in former windows in the north wall of the north transept and south wall of the south transept and the upper part of the west wall of the south transept. Also in cobels to the north wall of the north transept and north, east and south walls of the choir, east and west walls of the south transept and in part of the arches, vaults and elsewhere as described in the feature sets below.

The church stands in what was originally the inner bailey of the nearby castle and therefore probably began as a chapel serving the castle. The date of the church is not recorded but its ambition and the quality of its architecture and sculpture point to its construction during the period when Bishop Roger of Salisbury controlled the castle. It was probably built following the reconstruction of the castle after a fire in 1113 and probably around 1125-39.

Extensive survival of Romanesque sculpture.