The decoration in the nave consists of three distinct schemes dating from the 13th, 17th and 18th centuries. The earliest work (c. 1240) is set on a background of limewash on which red lines simulate masonry. The south clerestory panels contain painted imitation tapestries decorated with ornamental crosses, fleur-de-lys, rosettes, griffins, doves and fish.
Much of the detail escapes attention at first sight: a more careful examination of an apparently simple geometrical pattern of yellow and red rectangles reveals rows of fish hanging to dry. Close inspection, during restoration work, showed that outlines of birds as well as grids for the tapestry and roundel designs were incised into the plaster, and imprints of compass points could be seen.
Originally the 13th century decoration continued into the spandrels of the nave arcade in a series of roundels. Generally these have been overpainted in subsequent schemes, but half spandrels, whose design resembles a rose window, have survived at the east end of the nave.
The superimposed 17th and 18th century schemes depict ten of the tribes of Israel. Each roundel gives the tribe's name, has an appropriate emblem painted on a shield, and supplies a relevant biblical reference. In places elements of the 13th and 17th century decoration show through the subsequent reworking.