In the left-hand jamb of the north window, now much broken, another narrow door opens on a mural stair, 2 feet 6 inches broad, which, following the curve of the wall, and lighted by small loops, led up to the battlements, opening, on the way, upon the second floor, of which the floor and roof, both of timber, are now gone. This floor also had a fireplace, and a sort of magnified loop, which did duty as a door, and opened upon the battlements of the hall, and led also to a third garderobe, corbelled out above the other two. This has an open vent, while the shaft of the other two descends within the wall to a sewer, the arched mouth of which is just visible at the foot of the wall, outside. There seems also to have been a square-headed opening in the stair, to give a way to the top of the ward-curtain, of which the allure was 2 feet 6 inches wide, having a parapet of 3 feet, and a rerewall of 2 feet. As the parapet of the keep is gone, the stair terminates abruptly at the level of the rampart wall, where the wall is 7 feet 6 inches thick; and thence is a good view of the castle and town, and of one of the most lovely reaches of the Tees. In 1592 this keep was roofed with lead. The roof was probably always flat. Mortham Tower capped the north-west angle of the ward, rising from the rock high above the river. It is a mere fragment. It seems to have been of irregular plan, built to fit on to the hollow bend of an existing wall. When it was built, it was thought prudent to strengthen the wall by stout exterior buttresses. The original wall is Norman. The first built part of the tower seems to have been Early English, and its completion Decorated. The space between Mortham Tower and the keep was occupied by the hall and withdrawing-rooms, the latter being next the keep. The hall was on the first floor, as shown by its two windows in the curtain. These are of two lights, with a transom and trefoiled heads, and an oval quatrefoil in the head. They are placed in recesses with plain segmental arches, and side seats of stone. They are of the best Decorated period, and evidently insertions into an older wall, which has also been strengthened with Decorated buttresses. Between the hall and the keep were, on the ground-floor, passages leading on the left to what was probably a cellar below the hall, and on the right into the keep, while at its end is a small square-headed postern in the curtain, still in use. Above this passage was the withdrawing-room, placed between the hall and the state floor of the keep; and the window of this room, in the curtain, is the well-known bay which displays in its soffit the “bristly boar” of Richard III. The window is projected over the postern, upon bold corbels and is mainly of good Perpendicular date, but the superstructure has been altered and debased by some very poor Tudor work, similar to the window in the keep, and possibly due to Sir George Bowes. This was called “The Great Chamber” in 1592.