The Keep, also Norman, is an unusually perfect example of a shell keep. It is in plan a somewhat irregular polygon, 64 feet north and south by 74 feet east and west within the walls, which are about 8 feet thick. Within, it has twelve sides, of irregular lengths. Without are fifteen, and each angle is capped with a broad flat pilaster, all rising from a common plinth. At about two-thirds of the height there is a set-off, common to wall and pilaster; the latter has also a bold roll moulding. The wall is 20 feet high to the rampart walk. The parapet is gone. The keep stands upon the line of the curtain, which abuts upon it at opposite sides; so dividing it that there are eight facets outside the wall, and seven inside. The main entrance is by a full-centred arch of 7 feet opening, set in a broad, projecting buttress or pilaster towards the north-east. The arch of the actual doorway and of its inner recess is segmental. There was no portcullis, and the door had a stout wooden bar. Above the outer arch is a hood-moulding, with a light Norman ornament, said to be a restoration from the original. At present a straight steep flight of steps leads up to the door, and these, though modern, probably represent the original mode of approach. There is another and smaller door, diagonally opposite to the main door, to the south-west; this is quite plain, the arches segmental, the outer boldly splayed. The opening is 5 feet 6 inches wide. There are traces of something like a third door in the eastern face outside the curtain, opening from a bay in the wall. Opposite to this, in the west wall, is another bay, also 12 feet wide, but no trace of an opening. There are no loops in the wall of the keep, no trace of any buildings within its area, nor have any foundations been discovered there. It is pretty clear that any accommodation provided there was by means of timber structures placed against the wall, leaving an open court in the centre. There are indications, on the masonry, of an upper floor. Where the two curtains join the keep, each contains, at its rampart level, a mural chamber, about 6 feet wide by 12 feet long, the floor of which is about 10 feet or 12 feet from the ground. These chambers are choked with brambles and not accessible, but they have no door towards the ramparts of the curtain, and seem to have been entered from the upper part of the keep; that to the west is a garderobe, and has a loop and shoot upon the north or inner face; the other has a loop only, and that outwards: one of them is said to have been groined and vaulted, the vaults springing from columns in the angles. This is probably that towards the east, and it may have been an oratory, as at Arundel.