John sided with Simon de Montfort, 6th Earl of Leicester during the barons' rebellion against King Henry III, known as the Second Barons' War of 1263–64. He was summoned to the great parliament of January 1265, the first directly elected parliament in medieval Europe. During the battle of Evesham on 4 August 1265 he was wounded and taken prisoner. Released sometime afterwards he admitted to compound for his estates after the Dictum of Kenilworth.