Geoffrey fitz Peter, Justiciar since 1198, died on 14 October 1213. It is possible that his position at court had become strained over the years, in which case his death occurred at a convenient moment. John was about to embark on his long-planned bid for the reconquest of Normandy, and it was essential that he should entrust the government of England to an utterly reliable regent. Despite the return of the exiled clergy, the Interdict remained in force pending the agreement of compensation due to the church. Should the king's expedition end in failure, it was inevitable that the baronial grievances, which had already threatened to bring about rebellion in 1212, would boil over into open revolt.

Des Roches' commission as Justiciar is first implied in letters of 12 January 1214, and was explicitly announced to the country on 1 February. According to the Waverley annalist, John appointed the bishop to subject the magnates and to subdue the contumacious; by using his power unwisely, des Roches stirred up opposition to the king. The only other contemporary comment on his Justiciarship states that he was appointed ‘amidst murmurings from the magnates of the entire realm that an alien had been advanced over them’. Both of these accounts were written with hindsight, in light of the events of 1215. It would be wrong to accept untested the contention that des Roches abused his powers, or that from the outset his appointment was unpopular.