The Nave of the church, which is the main part of the building leading towards the altar, is predominantly 11th century. The north and south transepts were added in the 12th century by the Templars. The roof was originally a medieval Crown Post design, but this was renewed in the 1850s using Baltic fir and Horsham stone slabs.
Some of the architectural features have confused historians; for example, the square-headed perpendicular windows in the Nave date from 1827, although they have eroded to give the appearance of 15th or 16th century features.
Similarly, there is a 12th century doorway, with carvings on 11th century stones showing a 13th century depiction of Christ in Majesty surrounded by the symbols of the four evangelists. The stones were placed here in 1910.
Evidence of an 11th century window in the south wall suggests that the Templars may have rebuilt the wall using Saxon designs or by retaining much of the original wall.
The North Transept contains traces of a Norman window and a 14th century blocked door. The east wall was rebuilt in 1854, with the vaulted roof stemming from an unusual support (corbel) that has a face – sometimes referred to as a Saracen’s head.
The South Transept, which is lower than the rest of the church, was built in the late 12th century as a private chapel for the Templars. Signs of mediaeval fittings were noted in 1830, shortly after alterations (including an arch from the Nave) were introduced. The arch in the South Transept was modelled on the 12th century arch to the North Transept.
The font, moved from the west end of the Nave in 1827, has a 12th century Norman Sussex marble bowl. It originally had an elaborate 15th or 16th century cover, although this has now been lost.
The porch was added in the 16th century using 14th century materials, possibly from a former chapel. The bargeboard (to strengthen the roof) is a 14th century design, although it has been renewed.