This church was built within the walls of Portchester Castle around 1130. Originally it was intended to be part of an Augustinian Priory within the walls of the castle. There is evidence of a cloister and some domestic buildings present on the site, but shortly after it was completed the Canons moved to Southwick, perhaps because they lacked space to expand their monastery within the confines of the castle. The church was damaged by a fire set by Dutch prisoners of war in the castle in 1653 and was repaired in 1706 and further restored in 1888.
Adjacent to the church is a lovely cafe, which is highly recommended as a place to stop for a drink or lunch.