During the years 1275-81 Edward I (Longshanks) created a new land entrance, including a new moat so heavily fortified, any attackers would have to negotiate a drawbridge to the outer barbican or Lion Tower then via two more drawbridges separated by the Middle Tower with its two portcullises, they would then possibly reach the Byward Tower but only if they were extremely lucky. However, once there two more portcullises provided further protection; the western one, probably dating from the fifteenth century, and the oldest surviving device of its kind in the country, remains. The tower is the last defence before the outer ward and the fact that it was by the Warders Hall may be the origin of its name.
In the room, which is closed to the public is the winch for the portcullis. In 1953 wall paintings dating from late in the reign of Richard II (1377-99) were discovered. They are the only medieval paintings which survive at the Tower and, although damaged by Tudor restructuring, show a Crucifixion scene and emblems of royal heraldry.
The Chief Yeoman Warder and Yeoman Gaoler have their offices in this tower on one side of the arch and the main office for the Yeoman Body is on the other.