There is a second floor, reached by a well-stair in the square turrets, which ascend further to the roof, but it contains nothing of interest. The well-stair in the north-east turret leads to a door that opens on the north face, 20 feet from the ground, and which opened outwards, and was barred on the outside. The meaning of this is only explicable on the supposition that a bridge, or perhaps an embattled cross-wall, connected this door with the corresponding opening in Wakefield Tower, 18 feet distant. By this means a person leaving St. Thomas’s Tower, and barring the door behind him, would reach Wakefield Tower, and therefore the palace, and cut off pursuit. In the second floor of St. Thomas’s Tower is another door, above and similar to the first, which in like manner communicated with the top floor of Wakefield Tower; so that either there were two drawbridges, or a wall pierced by a mural gallery at 20 feet high, and with a rampart walk at its summit. St. Thomas’s Tower was, until lately, occupied by a water-engine, to the great injury of its walls. The upper rooms were cut up into lodgings by means of wainscot and lath and plaster. All has lately been cleared out, and the tower restored in good taste. St. Thomas’s Tower is attributed, and no doubt justly, to Henry III.; but, although the octagon chambers have an early English aspect, the grand arch, the staircase doors, and the windows towards the river are decidedly Decorated, though probably early in that style. If, therefore, this tower be of one date, it must be very late in the reign of Henry, but more probably it was completed and the grand arch turned in that of his son. The material is a rag-stone laid in uncoursed rubble masonry, like Beauchamp and Salt Towers, with ashlar dressings. The pool below was extensively repaired by Henry VIII. There is some reason to suppose that this was the tower that fell twice while being built. The curtain along this front is original, though capped and patched in modern times. It seems to have been about 20 feet high above the water, and from 12 feet to 14 feet on the inner side. In parts it was 12 feet thick; but the addition of brick casements in Tudor times, to enable the ramparts to carry cannon, prevents an accurate examination. It is no doubt the work of Henry III. From St. Thomas’s to Byward Tower is 160 feet. Byward Tower is the great gatehouse of the outer ward, and is placed upon the scarp of the west ditch, at its junction with the south ditch. It is in plan rectangular, 50 feet broad by 24 feet deep, and its two outward angles are capped by drum towers, 23 feet diameter, one quarter engaged, which rise out of the moat. Between them is a curtain of 14 feet, pierced by the main entrance. The towers, below the roadway, are solid; above it they are of three stages, and 49 feet high to the crest of the parapet, which, with most of the casing, is modern.