The chapel, which is on a small embankment to the north east of the castle, was rebuilt in stone in the early 15th century. It was modified from the late 15th to late 16th century, when a Perpendicular Gothic, five-light east window and transepts were added. Bucks' engraving of 1728, shows a short nave and a large six-light west window, and that the chapel was disused by this time, as it had no roof. The west façade of the chapel was later demolished and the chancel arch was built up to form a new one with a Gibbs surround. A bell-turret was added c. 1805. On the north and south sides of the chapel are two transeptal, semi-octagonal bays.