Gloucester was the natural leader of the lords of the Welsh march.  He was not only the hereditary lord of Glamorgan, but had received the custody of William of Valence’s forfeited palatinate of Pembroke.  He had shown self-control in separating himself so long from the marcher policy; and his growing suspicion of the Montforts threw him back into his natural alliance with them.  Even after the treaty of Worcester, the marchers remained under arms.  They had obtained from the weakness of the government repeated prolongations of the period fixed for their withdrawal into Ireland.  It was soon rumoured that they were sure of a refuge in Gloucester’s Welsh estates, and Leicester, never afraid of making enemies, bitterly reproached Earl Gilbert with receiving the fugitives into his lands.  Shortly after the breaking up of parliament, Gloucester fled to the march, and a little later William of Valence and Earl Warenne landed in Pembrokeshire with a small force of men-at-arms and crossbowmen.  There was no longer any hope of carrying out the Provisions of Worcester, and once more Montfort was forced to proceed to the west to put down rebellion.

By the end of April Montfort was at Gloucester, accompanied by the king and Edward, who, despite his submission, remained virtually a prisoner.  Earl Gilbert was master of all South Wales, and closely watched his rival’s movements from the neighbouring Forest of Dean.  It was with difficulty that Earl Simon and his royal captives advanced from Gloucester to Hereford, but Earl Gilbert preferred to negotiate rather than to push matters to extremities.  He went in person to Hereford and renewed his homage to the king.  Arbitrators were appointed to settle the disputes between the two earls, and a proclamation was issued declaring that the rumour of dissension between them was “vain, lying, and fraudulently invented”.  For the next few days harmony seemed restored.

Gloucester’s submission lured Leicester into relaxing his precautions.  His enemies took advantage of his remissness to hatch an audacious plot which soon enabled them to renew the struggle under more favourable conditions.  Since his nominal release, Edward had been allowed the diversions of riding and hunting, and on May 28 he was suffered to go out for a ride under negligent or corrupt guard.  Once well away from Hereford, the king’s son fled from his lax custodians and joined Roger Mortimer, who was waiting for him in a neighbouring wood.  On the next day he was safe behind the walls of Mortimer’s castle of Wigmore, and, the day after, met Earl Gilbert at Ludlow, where he promised to uphold the charters and expel the foreigners.  Valence and Warenne hurried from Pembrokeshire and made common cause with Edward and Gilbert.  Edward then took the lead in the councils of the marchers, who, from that moment, obtained a unity of purpose and policy that they had hitherto lacked.  He and his allies could claim to be the true champions of the Charters and the Provisions of Oxford against the grasping foreigner who strove to rule over king and barons alike.