This gate is in St. Thomas tower and was one of the most important river entrances to the Tower of London. It was built by Edward I and adopted the name of Traitors Gate because it was the entrance into the Tower for prisoners accused of treason, such as Anne Boleyn and Sir Thomas Moore.
Beauchamp Tower houses the "Prisoners" exhibition that contains extraordinary inscriptions on the walls made by people who were incarcerated here over the centuries. The inscriptions are protected with methacrylate and are really amazing.
This tower was built on the ruins of the Roman Wall by Henry III in 1238-41. It was used as a store of weapons and for domestic use. Legend has it that George Duke of Clarence, brother of King Edward IV, was imprisoned in the Tower and mysteriously executed.