The Saxon church was probably a wood or wattle building. The Domesday book lists two churches in Sudbourne, of which one may have been the church at Iken. The present church at Sudbourne was built in stone in the 12th century and there is a Norman arch above a blocked doorway in the south wall. The tower appears to have been added in the first half of the 14th century.
In 1621 the church is recorded as having a thatched roof. In 1676 the church was rebuilt after a fire. A sketch of the church in 1818 shows that the tower then had a short pyramid cap.
The church was completely restored in 1878-9, paid for by Sir Richard Wallace of Sudbourne Hall. The architect was Frederick Barnes, the contractor R S Smith and the stonemason Mr Frewer all of Ipswich. At this time the tower received a new roof and a lead-covered spirelet (known as a Hertfordshire spike).The south porch is now blocked, and you enter through the north one. Both have a pair of shields in the spandrels, one of passion symbols, the other of the Holy Trinity. The Trinity symbol is to the east in both cases.
At the time of the 1878 restoration, the interior was completely refurbished, with new benches and Minton tiles throughout. Two grand hatchments hang at the west end, a worthy frame for the tall tower arch and Norman font in front. One is to the Devereaux family, the Viscounts of Hereford and one to the Marquesses of Hertford. The heir of the fourth Marquess was Sir Richard Wallace and he in turn bequeathed to the state a considerable art collection, which today is known as 'The Wallace Collection'. Wallace also donated the organ here, in memory of his ancestors.
Up in the sanctuary is a large monument to Sir Michael Stanhope, who died in 1621. According to the inscription he sat at the feet of Elizabeth I for twenty years. In fact, he was a Privy Councillor, both to her and to James I. Now he kneels through all eternity in Sudbourne church. Below him is his wife all in black, and their daughters to front and back. They have been reduced to stumps, and she has lost her hands.
In the churchyard are many old gravestones. The best inscription is to Matthew Groom, who departed this life in 1769, at the age of 49. It reads in part:
The Boreas Blasts Neptunes Waves have tost me to and fro.
Yet spite of both by God decreed I Harbour here below,
Where I do now my Anchor lay with many of our Fleet.
Yet once again I must set Sail our Admiral Christ to meet.