Originally a cruciform, aisled Abbey church, now a parish church. Most of the E end of the nave and clerestorey and the first three bays of N and S arcades survive from the 11th-12thc. structure. The two W bays of the nave arcades are 13thc. and there is a 13thc. chamber, now a vestry, at the W end of the S side of the nave. The church was extensively restored in 1880 by Thomas Jobson Jackson, who rebuilt the 16thc. E wall, the clerestorey, S and N aisle walls and the N doorway. 12thc. sculpture is found on a reset tympanum and on some reset fragments from the original N doorway. The church has a 15thc. detached tower to the NW but very little survives of the conventual buildings.

The Domesday Survey records that the nuns of Elstow held land in Maulden, Wilhamstead, and Elstow from Judith, Countess of Huntingdon, the niece of William I. Judith had founded the Benedictine Abbey at Elstow after the Conquest, as an act of atonement for betraying her husband to the King according to popular legend. Judith's husband, Waltheof, had twice been involved in plots against William I and was beheaded in 1076 after the failure of the second plot.

VCH notes that Judith, or her daughter Maud, probably gave the church at Kempston to Elstow Priory. It is recorded among the possessions of Elstow by 1218 (VCH, 304).

The confirmation charter of Henry I, granted c.1126, names among the Abbey benefactors: Nicolas and Richard Busset, Nigel de Stafford and Countess Maud, daughter of Judith and wife of Simon de Senliz.

The conventual church was also the parish church of Elstow although a separate chapel was built in the churchyard in the 14thc. and dedicated to St Helena.

VCH records that the nuns of Elstow were granted a yearly fair, which caused some discontent amongst the Bedford Burgesses (VCH, 281).

M. J. Buckley (in Wigram, 197) describes the presence of small plaits on the outer robes of the figure of Christ and a 'crucifixion nimbus' around his head. The Antiquary has an illustration of the tympanum by Bailey, taken from the L of the carving and therefore obscuring St Peter's key, which is shown as a long staff. The book is missing from the depiction of St Paul and he appears to be bald! The drawing does indeed show Christ with a halo with cross arms, within a pointed mandorla. However, an etching by Fisher of 1820 of the N doorway and tympanum shows that the upper part of the head of Christ is missing, and as Bailey's drawing probably post-dates the c.1880 restoration, the 'crucifixion nimbus' is either a restoration now gone, or was an embellishment by Bailey.

Bailey, Pevsner, and VCH propose that the figure of Christ in Majesty is flanked by St Peter on the L and St John on the R. The source for this attribution seems to be Buckley. As St John is usually represented as youthful and clean-shaven it seems more likely that the R figure is St Paul, who is usually described and depicted as bearded. The tympanum figures, especially in the tilted heads of the saints and the fall of drapery, may be generally compared with carvings in the S porch at Malmesbury Abbey. Pevsner draws a comparison with Moissac, presumably meaning the tympanum over the S doorway of the porch of L'abbaye Saint-Pierre. The tympanum is carved with a Christ in Majesty with angels, and the four winged evangelist symbols holding books, with carvings of the 24 elders below. The tilted heads of the elders are similar to those of St Peter and St Paul at Elstow. The comparison with Malmesbury is closer however.

Fisher's etching shows the second and third order R capitals and first and second order L imposts of the N doorway weathered away. The impost mouldings are drawn with a fine roll between wedges, as opposed to those of the restored doorway, which have a thick roll between wedges. The left capital of the tympanum has a recessed shield and the outermost order of the tympanum arch is not depicted in the print.

Lyson describes the N doorway, but not in detail, noting simply that 'the N door is of Norman structure; some of the columns are square and very massy and most of the arches circular' (Lyson, 81).

Archaeological evidence suggests that the E end of the chancel was apsidal in the original 11thc. church although squared off in the late 12thc., and that the chancel itself was unusually long. The S transept appears to have been continued eastward alongside the chancel, perhaps forming an aisle (Baker, 1971). Pevsner suggests that this was a Lady Chapel. The originally 16thc. wall blocking the E end was inserted in the bay before the crossing.