St Peter's has an aisleless nave and chancel, both rendered, and a round W tower of flint. The nave has very thick walls, probably 11thc., which have been reduced in thickness in their lower parts inside in order, according to Cautley, to increase the available width. There are 13thc. N and S doorways; the N under a porch, the S now giving access to a 19thc. flint vestry. On the exterior, above the S vestry, can be seen a chip-carved arch, identified by Pevsner as 'the surround of a lavish window.' The chancel arch is wooden, and the chancel largely a rebuilding of 1862. The elaborate tower arch is 19thc. neo-Romanesque, but an original chip-carved voussoir is reset above it. The tower is of three storeys. In the first is a 19thc. neo-Romanesque W window; the second is articulated as a band of blind arcading with plain 12thc. lancets at the cardinal points (the E visible inside the church). The third storey has 12thc. double bell-openings at the cardinal points. The tower is capped by an unusual early-16thc. octagonal parapet of brick with triple-stepped merlons. The font, while 13thc., is of Sussex marble and of a type common in Sussex. It may be an import. A photograph is included, but no description. Romanesque sculpture is found in the bell-openings of the tower, the arch in the S wall of the nave, and the voussoir above the tower arch.

The Domesday Survey listed four holdings in Thorington in 1086. Two-and-a-half carucates in Thorington and Wenhaston were held by six free men from Count Alan, the holding containing a church with 10 acres of free land and half an acre of meadow. A further 30 acres were held by Northmann from Roger Bigod, and under him (Northmann) the land was held by Aelfgifu, a free woman. A third holding of 2 carucates was held by Godfrey de Pierrepoint from William de Warenne, but the land was claimed by Robert Malet. Finally a manor of 3 carucates was held by William de Bouville from Geoffrey de Mandeville, and this also included a church, with 8 acres of land.

Blyth Valley Team Ministry, i.e. Blyford, Bramfield, Chediston, Halesworth, Holton, Linstead Parva, Spexhall, Thorington, Walpole, Wenhaston and Wissett.

Taylor and Taylor date the lower part of the tower, including the blind arcading, to the Anglo-Saxon period or 'at latest Saxo-Norman'. The blind arcading, executed entirely in flint, has parallels at Tasburgh and Haddiscoe Thorpe (both Norfolk). This in contrast to what is certainly 12thc., i.e. the lancets and bell-openings. They further point out that the lancets are not placed symmetrically with respect to the blind arcading, suggesting that they are later insertions. Pevsner takes a similar position. The chip-carved decoration of the nave suggests date around 1100 or slightly earlier, and the present author is inclined to include the lower part of the tower in the same campaign, agreeing that the lower lancets and the bell-openings are later insertions ofc.1170-80.