Under the whole of the choir is a crypt entered from the transept, and in the angles between the transepts and the choir are towers, the lower stages of which are open to the transepts and form chapels, whose altars stand in small apsidal projections on the east face of the tower. A door on either side of the sanctuary leads by a staircase in the thickness of the wall to rooms above the chapels in the tower. The entrance to the choir is through the old rood-screen by doors on either side of the altar, and by doors in the parcloses, reached by long flights of steps in the transepts. The nave is divided into three groining bays, each bay subdivided and having two arches into the aisles. The western choir has one bay and a five-sided apse. On either side of it is a narrow passage leading to staircases which lead to rooms above some chapels, which have now to be mentioned. They form the base of towers at the west end of the aisles, but project considerably beyond them: only one of these towers has been built; the other is carried up and finished externally as though it was a transept, and produces at first some confusion when seen from the exterior. These tower chapels are very curious. That on the south side has a circular central shaft, decreasing in size to the capital, and the vaulting has four ribs springing from corbels in the angles of the chapel in a semicircular arch to the cap of the column, and there are no other ribs. In the _east_ wall is a small semicircular recess, in which still stands the original altar with a double footpace. The north tower chapel is almost exactly like the other, save that it has a polygonal central shaft, and the recess for the altar is rectangular. Both chapels are lighted with small round-headed windows in their western faces. From this description it will be seen that the ground-plan of this church is so curiously alike at its eastern and western ends, as to be somewhat confusing at first.