The medieval building, dedicated in 1188, was cruciform in shape, with a central tower, which was used as a lookout point and lighthouse, over the crossing. Of the original building, only the chancel and the transepts remain.
The establishment of the Diocese of Portsmouth in 1927 brought about significant changes with plans to extend it. Finally, in January 1990, a fourth bay of the nave, western towers, tower rooms, rose window, gallery, ambulatory, together with the stone altar beneath Nicholson's tester and the new stone font were added.
