The church is substantially late medieval and Victorian, retaining no evidence of the Norman structure to which the font may have belonged.
Warnham is not mentioned in the Domesday Book, but before 1204 William de Braose gave the church to Rusper Nunnery (confirmed by Bishop Seffrid II, 1180-1204, VCH vol II, 63ff). Rusper Nunnery also held the churches of Ifield, Selham and, from 1231, Horsham.
The medieval dedication is noted in a will of 1505: Sussex Record Society, 45, p.296.
(Location: W end of nave, to N of doorway.) A square basin of Sussex marble carved with five round-headed shallow arches on the E, S and N faces, and a central uncarved square area flanked by one and half arches on the W face. Rather than suggesting that the W face is unfinished, the square area indicates that it abutted a wall or pier originally. The outlines of the arches are bevelled and beneath the arcading the bowl is chamfered. A horizontal break runs around the bowl at the springing of the arches, and there are central vertical joins on the S and W sides. The interior is circular and lead-lined. The bowl is supported by one thick central shaft and four slender angle shafts, also Sussex marble, which seem to have been renewed or heavily retooled. They sit on a square modern plinth.
|h. of bowl||0.325 m|
|int. dia.||0.60 m|
|w. of bowl (bottom)||0.71 - 0.72 m|
|w. of bowl (top)||0.755 - 0.76 m|