After the death of William Mauduit in 1267, the title and castle passed to his nephew William de Beauchamp, 9th Earl of Warwick. Following William's death, Warwick Castle passed through seven generations of the Beauchamp family, who over the next 180 years were responsible for most of the additions made to the castle. In 1312, Piers Gaveston, 1st Earl of Cornwall, was captured by Guy de Beauchamp, 10th Earl of Warwick, and imprisoned in Warwick Castle until his execution on 9 June 1312. A group of magnates lead by the Earl of Warwick and Thomas, 2nd Earl of Lancaster, accused Gaveston of stealing the royal treasure. Under Thomas de Beauchamp, 11th Earl, the castle defences were significantly enhanced in 1330–60 on the north eastern side by the addition of a gatehouse, a barbican (a form of fortified gateway), and a tower on either side of the reconstructed wall, named Caesar's Tower and Guy's Tower. The Watergate Tower also dates from this period.