Jean de Gisors, a wealthy Norman merchant and lord of the manor of Titchfield, provided land in c.1180 to build a chapel dedicated to the martyred Thomas Becket. It was built to serve the growing community that had settled around the harbour mouth and the work was entrusted to the monks of Southwick Priory.
The medieval building was cruciform in shape, with a central tower. It was under construction by 1185, with the chancel and nave consecrated in 1188. By 1196, the transepts, altars and the churchyard were also consecrated. Sadly the original nave has not survived, it was damaged in 1642 during the Civil War when the Parliamentary forces attacked the town.
The chancel is of two main bays, with the arcade containing pairs of small pointed arches, within larger arched frames. The intermediate piers between each pair of smaller arches are of black marble. The original Purbeck marble piers and some of the round capitals have been renewed. The piers between the main bays are octagonal with simple moulded capitals and arches formed with cluster shafts.
The transepts retain some Norman features, such as lancet windows and arched recesses, with the later northern transept containing the slightly later cusped windows and arch.
Sadly, this is all that remains of the medieval church, but enough survives to indicate it was a church of the finest quality. It is important in reflecting architecturally the transitional period, with close parallels at Chichester Cathedral and Boxgrove Priory.
The chapel of St Thomas became a parish church in the 14th century and 600 years later the cathedral church of Portsmouth. During this time there were a great many alterations, not least of all in the 20th century, which saw the final completion of the church. The newly finished cathedral was consecrated in 1991.
Pevsner, N., and Lloyd, D., 1967. The Buildings of England, Hampshire and the Isle of Wight (London, Penguin), 393-404