Following this, in January 1371 the Prince returned to England, while Pembroke remained in France and continued to prosecute the war, now alongside Gaunt. Together they besieged Montpaon from January to February 1371, after which, Pembroke himself was recalled to London in order for him to attend the coming parliament to which he had been summoned on 8 January earlier that year. By this time, Pembroke dominated the court; although he was unable to persuade the King to assist him in Pembroke's dispute with Lord Grey of Ruthyn.At this parliament, which sat from February to March 1371, Pembroke was appointed a trier of petitions. His business at this parliament was not purely administrative; Pembroke appears to have been the main leader of an anti-clerical parliamentary faction which politically attacked the king's clerical ministers. At least, so he was portrayed in some contemporary chronicles. His actions have been described as radical. As a result of this assault, William of Wykeham and Thomas Brantingham (the Chancellor and Treasurer, respectively) were forced to resign, with their positions taken by laymen. Sumption suggests that the immediate cause for Pembroke's attack was his recent experiences at the front line, in "frustrating and underfunded campaigns" whilst, at home, as the writer of a contemporary French tract colourfully put it, "the clergy reposed peacefully beneath shady canopies elegantly scoffing fat delicacies"!