St James's has a nave with three-bay N and S aisles, the N arcade late 12thc., the S c.1200. The chancel and its arch are 13thc. and there is a N chapel. The E end of the chancel is all 14thc., so it may have been extended. At the W end is a 13thc. tower with a recessed Perpendicular spire with two rows of lucarnes. A stained glass window at the E end of the S aisle was dedicated in 1983 to the 384th(H) Bombardment Group of the 8th US Airforce, which was stationed at Grafton Airfield during World War II. The nave arcades are the only Romanesque features.

In 1086 Robert Blund held three hides in Grafton Underwood, and a further half-hide was held by Reginald of Eustace, who was said to occupy the land by force to the detriment of the Church of Ramsey.

Benefice of Cranford with Grafton Underwood and Twywell.

The later S arcade has round-headed arches with a very pronounced chamfer on the inner order. It should be noted that the use of capitals with circular abaci like this would be impossible without such a deep chamfer.