The chapel tower, forming part of the east curtain, deserves particular attention. It is an oblong building, springing from a rectangular base; but, as the two outer or eastern angles are formed by buttresses, each of which is a half pyramid, cut diagonally, the plan of the upper part is an oblong, with the two eastern angles removed so as to form an apse. As this tower projects some way down the steep, its outer face is 56 feet high and its inner only 20 feet. Its top is 24 feet lower than that of the contiguous south-east tower. Against the south side of the chapel tower is a small square projection containing a vestry. This does not rise to the clerestory. The chapel tower has three floors, all ceiled with timber. The interior is 26 feet from the altar to the west end, and 18 feet broad. The east wall is 6 feet thick; the west wall, 3 feet. In the south-east corner is a mural gallery, leading to a sewer chamber below the vestry. In the north-east corner is a well-stair. The ground floor is below the level of the inner ward, and is entered by a curved stair from the adjacent hall. The next, or first floor, is on the level of, and entered directly from, the hall. Above this, and on the rampart level, is the chapel. This includes two tiers of windows, the upper being a clerestory, and is entered by a west door. The east window is common to both tiers. It is a long, narrow, and acutely-trefoiled loop, set in a broad recess, which nearly occupies the whole east bay of the apse, and has a flat drop arch with a plain rib. In the face next south of the altar-place is a small trefoiled piscina, and next to this a broad recess or sedile under a drop arch. On the south side, a small, acutely-pointed door leads to the vestry, and west of this is another recess, with a flat drop arch, and in it, close to its east side, a loop, long since blocked up, intended to defend the nook between the vestry and the south-east tower, and to rake the adjacent curtain. There is also a trefoiled loop in the north wall, and a door long closed up. The clerestory is lighted by nine windows, three on each side, and three, including that to the east, in the apse. They are all alike—long, narrow, acutely-trefoiled openings, within broad recesses, plainly ribbed, and with flat drop arches. All rest inside upon a string, a filleted half round, which dips to pass under the east window. Between each pair of windows is a plain corbel block for the roof timbers. There is nothing, save the battlements, above the chapel. The walls have been stuccoed. The west wall has neither ashlar dressings nor string course, and is of different date and inferior work to the rest of the tower.