 As a result, he was unpopular, and was heavily involved in the Second Barons' War, supporting the King and Prince Edward against the rebels led by Simon de Montfort.After the final defeat of the rebels at the Battle of Evesham in 1265, William continued to serve Henry III, and then Edward I, until his death in 1296.William's eldest surviving son, Aymer (c. 12651324), succeeded to his father's estates, but was not formally recognized as Earl of Pembroke until after the death of his mother Joan in 1307.