The moat, some hundred feet wide at its widest, was formerly flooded with the waters of the Thames, and is now used as a parade and playground for the garrison. It dates back to the Norman Conquest, and was deepened by William Longchamp, Bishop of Ely in the reign of Richard I. Death was the penalty for bathing in its waters in the reign of Edward III.—a severe law, but one may hope that a sentence so severe for so apparently trivial an offence was not actually enforced; perhaps death was the result of some one having taken his bath in the Tower moat in the unsanitary days of Edward III. When the Duke of Wellington was Constable of the Tower, he had the moat filled up to its present level, and the river waters which had, daily, during eight centuries supplied it by their ebb and flow, ceased to encircle the old walls. Doubtless the fortress gained in healthiness by the change, but from a picturesque point of view the general effect of the building has been greatly lessened since the days when the old walls and bastions were reflected by the waters of the moat, nor can its towers and turrets appear so effective as when they were mirrored in surrounding water. Four bridges with their causeways spanned the moat. To the west stood the Lion Gate bridge; a second was (and still is), that of the Middle Tower; the third faces the river at Traitor’s Gate under St Thomas’s Tower; and the fourth is that at the eastern extremity of the fortress, near to a dam which connected the tower above the Iron Gate with the tower formerly called Galleyman’s Tower, or “the tower leading to the Iron Gate.” Middle Tower, the first by which the present visitor to the Tower enters the fortress, has been greatly modernised in its upper part. Since the destruction of the Lion Tower it has become the first gate of the Citadel, its name having been gained by its original position between the Lion and Byward Towers, to the latter of which it formed the outwork: it protects the western and landward approach to the fortress. Originally the Middle Tower was coated with Portland stone. It has a double portcullis, which can still be used if required. In front of this Tower, in mediæval days, stood a drawbridge, of which however, no trace remains, the moat now being spanned by a bridge of stone 130 feet in length and 20 feet in width at its narrowest part.