St Mary’s is a large Gothic church. Bilson describes it as having 'a chancel of five bays, with north and south aisles, and a sacristy to the north side of the north aisle; transept, of which the northern arm has three bays and a large chapel on its eastern side, and the southern arm has three bays and an aisle on its eastern side; crossing with central tower; nave of six bays, with north and south aisles; and south porch' (Bilson 1920, 363). There is, comparatively, very little left of the Romanesque period.

Seen from the S nave aisle, on the S wall is a round-headed chevron arch now positioned as the relieving arch to the main entrance; in the N transept is a 15thc. arcade that reused existing stonework to make its three pointed arches. Along the base of the chancel arcades the line of the 12thc. chancel wall is marked by a kerb and remnants of pilaster bases. There are a few fragments in the Priest’s Room (view by appointment only).

This was one of three parish churches in the medieval town. The manor was held by the Archbishops of York until 1542. Church founded ‘by the mid C12’ (Pevsner & Neave 1995, 294). John Bilson (Bilson 1920, 364), dates the voussoirs at the S nave doorway to the last years of Archbishop Thurstan, who died in 1140.

John Bilson says that 'whether there was a church on this site before the twelfth century or not, it is certain that the earliest fragments which have survived represent the original plan out of which the existing church has grown'. In the chancel are the stubs of buttresses of the original 3-bay chancel. He believes the chevron arch in the S aisle was from the original S doorway, moved in the 13thc.. After about 1300, the work is in Tadcaster (Magnesian) limestone, whereas earlier it is in Newbald (Oolitic) stone (Bilson 1920, 364-5).

Bilson suggests the original plan of the church was chancel, nave and central tower: there were no aisles, and he believes no transepts initially (Bilson 1920, 367).

North Transept arches

Briefly, John Bilson says that all three arches in the N transept were remade in the 15thc. from earlier work; that the chevron ‘hood’ was originally an order, and that all the arch material on the W face could be contemporary (Bilson 1920, 367-8); to the chapel on the E side, however, the work is of the later period. There follows a fuller version of his remarks on the reset arches of the north transept:

'Beyond the outer order, on the side next to the transept [i.e., W face of the arch] is a moulding 6 inches in depth, which now serves as a hood-mould. This bears a chevron ornament, of two rolls with a fillet between them, and a pellet in the sunk spandrel above... this zigzagged hood was not a hood-mould originally, but an arch order, adapted as a hood when the arches were re-set in the fifteenth-century reconstruction.'.. The character of the detail of arch-orders and 'hood' indicate that the original arcade of which they formed part dated from the latest years of the twelfth century' (Bilson 1920, 367-8). The transept was initially added to the church in the end of the twelfth century; the arches 'now spring from piers which belong to the mid fifteenth-century reconstruction' (Bilson 1920, 409).

'The arch orders are badly fitted, and the curves are distorted - results which do not appear to be altogether due to settlement, but rather to the way in which they were reset, possibly to slightly different curves and spans from the original ones' (Bilson 1920, 410). He seems to be saying that the arches were pointed even in their first installation.