Warwick was not personally pledged to Gaveston’s safety, though, as one of the confederates, he was clearly bound by their acts.  His seizure of Peter was only warrantable by the, fear that Pembroke, with his royalist leanings, was likely to play the extreme party false; but in any case Warwick was as much obliged as Pembroke to observe the terms of the capitulation.  Neither Warwick nor his allies took this view of the matter.  They rejoiced at the good fortune which had remedied the disastrous capitulation of Scarborough, and resolved to put an end to the favourite without delay.  Lancaster was then at Kenilworth; Hereford, Arundel, and other magnates were also present, and all agreed in praising Warwick’s energy.  On Monday morning, June 19, the three earls rode the few miles from Kenilworth to Warwick, and Earl Guy handed over Peter to them.  They then escorted their captive to a place called Blacklow hill, about two miles out of Warwick on the Kenilworth road, but situated in Lancaster’s lands.  The crowd following the cavalcade was moved to tears when Peter, kneeling to Lancaster, cried in vain for mercy from the “gentle earl”.  On reaching Blacklow hill, the three earls withdrew, though remaining near enough to see what was going on.  Then two Welshmen in Lancaster’s service laid hands upon the victim.  One drove his sword through his body, the other cut off his head.  The corpse remained where it had fallen, but the head was brought to the earls as a sign that the deed was done.  After this the earls rode back to Kenilworth.  Guy of Warwick remained all the time in his castle.  He had already taken his share in the cruel act of treachery.  It was, however, important that Lancaster should take the responsibility for the deed.  Four cobblers of Warwick piously bore the headless corpse within their town.  But the grim earl sent it back, because it was not found on his fee.  At last some Oxford Dominicans took charge of the body and deposited it temporarily in their convent, not daring to inter it in holy ground, as Gaveston had died excommunicate.

The ostentatious violence of the confederate earls broke up their party.  Aymer of Pembroke, indignant at their breach of faith, regarded the whole transaction as a stain on his honour.  He besought Gloucester’s intervention, but was only told that he should be more cautious in his future negotiations.  He harangued the clerks and burgesses of Oxford, but university and town agreed that the matter was no business of theirs.  Then in disgust he betook himself to the king, whom he found still surrounded with the Beaumonts, Mauleys, and other friends of Gaveston, against whom the ordinances had decreed banishment.  Warenne, whose honour was only less impeached than Pembroke’s, also deserted the ordainers for the court.  Edward bitterly deplored the death of his friend.  He gladly welcomed the deserters, and prepared to wreak vengeance on the ordainers.