The work which excited the greatest interest was the construction of the River Gate facing on to the Lower Wharf. Twice during its building the structure collapsed, and among the London citizens, who viewed the Tower and all its works with a fearful suspicion, the repeated failure was ascribed to the direct interposition of St. Thomas of Canterbury, who intervened to protect the liberties of his native city.
The saint, however, according to the story, was temporarily pacified by the inclusion of a Chantry dedicated in his honour in the third edition of the structure.
The Gate, since called St. Thomas's Tower, or the Traitors' Gate, with its enormous inner arch, was apparently again reconstructed at the end of the thirteenth century. The arch, 61 feet wide, is a remarkable piece of construction, each stone being notched or joggled into its two neighbours, to ensure cohesion.
This work was only one of the numerous alterations made to the Tower by Edward I. Large sums of money were spent during twelve years in digging the existing great ditch or moat round the defences, and in building the retaining wall on its inner side.
The earlier ditch of Longchamp had probably skirted the inner line of defences, but the new and much broader ditch provided a narrow court or bailey running along the outside of these walls on the site of the earlier ditch. The clay from the excavations was sold at regular intervals to the tile-makers of East Smithfield.
The construction of the new ditch necessitated the rebuilding of the Tower entrances to the west and east, and the existing buildings of the two western gatehouses (the Middle and Byward Towers) are substantially works of this age.
Of the less important eastern approaches only the Develin Tower or Gate survives, and this has been denuded of all character. Edward I was the last of the great builders at the Tower; his successors contented themselves with minor alterations and reconstructions.
Later, about 1350 the postern from the Palace to the Tower Wharf, called the Cradle Tower, was built, and towards the end of the same century the inner Gatehouse, called the Bloody Tower, was added or rebuilt. Both this and the Byward Towers retain their old portcullises and the machinery for raising and lowering them.