Like most East Anglian Perpendicular churches, it underwent a fairly substantial 19th Century restoration, but it is a harmonious interior, full of light, and retaining some old woodwork, although the great nave roof is part of the restoration. The font is 15th Century, made new for the new church, and the panels hold old shields with the symbols of some Saints, the Holy Trinity and the Instruments of the Passion.

But the star of the show here is obviously the fine collection of 15th Century stained glass. The fragments have been reassembled in two windows in the north aisle, and like the font were probably made for the new church. The figures include most of a feathered angel playing a harp, as well as a fine St Catherine. There are two bishops, one given the head of an old man by its restorers. Fragments include the head of a Christ Child and the arm and staff of the St Christopher who is carrying him. The are the two hands of an infant Christ as Salvatore Mundi, one holding an orb. An ugly head wearing a cowl was probably intended by our anti-semitic forebears as a Jew at the flagellation or crucifixion of Christ.

This medieval splendour must not distract us from the fact that Guestwick has that rarest of beasts, a very fine millennium window. It depicts the wildlife of the parish, and is the work of Adam O'Grady, who installed it over a period of nearly ten years. The great fortune of Guestwick is that he lives in the parish.