The massive buttress supporting the choir wall, at the head of the steps to the undercroft, is divided into stages by a flat niche or panel with side-shafts of Purbeck marble. This was found, in 1840, to contain a mural painting of the Crucifixion, with the Blessed Virgin and St. John at the foot of the cross. The principal face below had a gigantic representation of the Madonna and Child, more than 12 feet in height. At about the same time the elegant little doorway at the west end of the aisle was found. It could not be reopened, but its mouldings were uncovered. It is of the Early English period and has a dripstone ending in a bishop's and a female head. In this aisle, on its north side, is the tomb thought to be that of Bishop John de Bradfield, who is stated by Edmund de Hadenham to have been buried on the south side of the church, "juxta ostium excubitorum," _i.e._, by the watchers' door. It has a very battered figure of a bishop in low relief. The #Crypt#, or undercroft, is approached by the flight of steps in the south choir aisle, but its original entrance seems to have been on the other side of the church. Just inside the doorway, with its peculiar flatly-pointed head under a pointed arch, there is, to the right, a small square cell which may have been used as a place of confinement. The crypt is one of the finest in England, and the later, main portion of it is the last great work of the kind carried out in this country. The two western severies, consisting of the old Norman work, are now shut off to contain the organ bellows and their machinery, and the whole southernmost aisle has been partitioned off into a series of new vestries, erected with the proceeds of Dean Hole's recent lecturing tour in America. The whole width is divided into seven aisles, three under the choir proper and two under each transept. Each seems to have had an altar at its east end; several piscinas still remain. The main walls above are carried by heavy masses of masonry, which rather break the vistas, while other masses help the usual columns to bear the steps on which the altar stands.