The church comprises an aisleless nave, chancel and W tower with a memorial chapel attached to the chancel on the N, and the vestry attached to the nave on the N. In the 12thc. the church consisted of an aisleless nave and chancel. The W tower was added in the 15thc. and the Lytton chapel, which abuts the chancel, was added in the 16thc. The E and S walls of the chancel were rebuilt in the 19thc. by Edwin Lutyens. The vestry on the N side of the nave is 19thc. and the attached kitchen and utility rooms are 20thc. A plain, blocked 12thc. window with roll -moulded jambs survives in the N wall of the chancel. A S doorway to the chancel and two flanking round-headed windows were replaced in Lutyen’s restoration. Simple sculpture survives on the chancel arch and on a section of cross-shaft reused as a quoin stone on the SE angle of the chancel. Much of the original walling has been rendered, although a small section on the N wall of the nave (W end) has the original flint walling exposed. The tower is of flint as are the 19th and 20thc. alterations. Lutyen’s walling is of knapped flint. The church is located in the grounds of Knebworth House.

The advowson of the church has always belonged to Knebworth manor. At the time of DS the manor belonged to Eudo Dapife, son of Hubert de Ryes. In the mid-12thc. it passed to Warine Fitz Gerold and his successors.