Somerton is situated 20 miles due N of Oxford, standing high on the E bank of the Oxford canal in the valley of the river Cherwell. The original church is known to have been in existence soon after the Norman Conquest, and a N aisle was added in the early C13th. The present church is largely C14th and comprises a chancel, clerestoried nave, N aisle, S chapel and W tower. In the 16thc. the S aisle was converted into the Fermor Chapel, and new windows were inserted. The blocked arch of a Romanesque doorway is visible in the S exterior wall of the nave, also internally as a rere-arch.

The church was in existence by 1074 when a grant was made of the tithes of Northbrook, part of the parish. In 1107 the church and its tithes were given to the alien priory of Cogges, near Witney (VCH).

The external proportions of the blocked doorway in the S nave wall suggest that it would have been taller than visible now and that it probably extends below ground level.

The N arcade of the church has been referred to as late C12th or early C13th work (VCH). The author agrees with Sherwood and Pevsner who believe it to be early C13th work. The four pointed arches, plain and chamfered, are supported by three plain round piers with C13th capitals. They appear to lack bases and stand on square, massive plain chamfered plinths.