As bishop, Cantilupe identified himself with the party of ecclesiastical reform, which was then led by
Edmund Rich and
Robert Grosseteste. Like his leaders he was sorely divided between his theoretical belief in the
papacy as a divine institution and his instinctive condemnation of the policy which
Pope Gregory IX and
Pope Innocent IV pursued in their dealings with the English church. At first a court favorite, Cantilupe came at length to the belief that the evils of the time arose from the unprincipled alliance of crown and papacy. In 1240 Cantilupe conducted the significant
Synod of Worcester, advancing many reforms for the church. Cantilupe raised his voice against papal demands for money, and after the death of Grosseteste in 1253 was the chief spokesman of the nationalist clergy. At the parliament of
Oxford in 1258 he was elected by the popular party as one of their representatives on the committee of twenty-four which undertook to reform the administration; from that time until the outbreak of civil war he was a man of mark in the councils of the baronial party. During the war he sided with
Simon de Montfort, 6th Earl of Leicester and, through his nephew,
Thomas de Cantilupe, who was then
Chancellor of
Oxford University, brought over the university to the popular side. Cantilupe was present at the
Battle of Lewes and blessed the Montfortians before they joined battle with the army of the king; he entertained de Montfort on the night before the final rout and defeat of the
Battle of Evesham. During Montfort's rule Cantilupe appeared only as a mediating influence; in the triumvirate of electors who controlled the administration, the clergy were represented by the
Bishop of Chichester. ==Death and legacy==