The originally pre-Conquest church comprises, chancel, nave with N and S aisles and S porch, and W tower. The thick-walled nave is 11thc and it has a two-bay 12thc S arcade. There are traces of a round-headed window at the W end of the S aisle wall. The chancel was rebuilt in the early 13thc and the three bay N arcade was added at this time. The W tower is 14thc and the S porch 15thc. A clerestory was added in the 16thc. and N and S chapels in the 19thc. The chancel was restored in 1898. What is thought to be the decorated impost from the original S doorway now forms the W impost of the pier of the S arcade. A pre-Conquest carving of a Crucifixion is set into the S side of the wall of the S arcade. This probably formed part of a Rood (RCHME, 1910, 224; Pevsner and Cherry 1977, 372). The carving is discussed in detail in the Corpus of Anglo-Saxon Stone Sculpture (CASSS 1995, 240-41). Romanesque sculpture is found on the S doorway.

Before the Conquest Walkern was held by Alwin Horne and the overlord was King Edward. After the Conquest, Deormann of London was Lord and also tenant-in-chief (Open Domesday: http://opendomesday.org/place/TL2826/walkern/).

The Corpus of Anglo Saxon Stone Sculpture comments on the Crucifixion figure and the moulded impost in some detail, identifying both as pre-Conquest 11thc. The CASSS compares the moulding on the impost with similar examples at Little Munden in Hertfordshire, and Dartford and Orpington in Kent. Both Smith and the CASSS state that the moulded impost would have been from the original 11thc. S doorway (Smith 1973, 33; CASSS 1995, 241). The opposing impost would have been removed when the S wall of the original nave was cut into to form the S arcade.