In front of the inner gatehouse is one of Henry VIII's additions - a semi-circular gun battery with a covered fighting gallery facing the ditch. During the invasion scare of the 1540s, Henry thickened the inner curtain to support artillery. The wide parapet is partly carried on arcades and there is a ramp for wheeling up cannon. Within the inner bailey rises a great keep, which is virtually a cube. The keep is freestanding though very close to the curtain. As was originally conceived, each of its four stories contains a single large room.