his favourite Piers Gaveston. When Parliament decided that Gaveston should be exiled the king was left with no choice but to comply. Edward engineered Gaveston's return, but was forced to agree to the appointment of Ordainers, led by his cousin Thomas, 2nd Earl of Lancaster, to reform the royal household with Piers Gaveston exiled again. When Gaveston returned again to England, he was abducted and executed after a mock trial. The ramifications of this drove Thomas and his adherents from power. Edward's humiliating defeat by Bruce at the Battle of Bannockburn in 1314, confirming Bruce's position as an independent king of Scots, leading to Lancaster being appointed head of the king's council. Edward finally repealed the Ordinances after defeating and executing Lancaster at the Battle of Boroughbridge in 1322. The French monarchy asserted its rights to encroach on Edward's legal rights in Gascony. Resistance to one judgement in Saint-Sardos resulted in Charles IV declaring the duchy forfeit. Charles's sister, Queen Isabella, was sent to negotiate and agreed a treaty that required Edward to pay homage in France to Charles. Edward resigned Aquitaine and Ponthieu to his son Edward, who travelled to France to give homage in his stead. With the English heir in her power, Isabella refused to return to England unless Edward II dismissed his favourites, and she became the mistress of Roger Mortimer. The couple invaded England and, with Henry, 3rd Earl of Lancaster, captured the king. Edward II abdicated on condition that his son would inherit the throne rather than Mortimer. Although there is no historical record of the cause of death, he is popularly believed to have been murdered at Berkeley Castle by having a red-hot poker thrust into his bowels. A coup by Edward III ended four years of control by Isabella and Mortimer. Mortimer was executed. Though removed from power, Isabella was treated well, and lived in luxury for the next 27 years. Conflict with the House of Valois In 1328 Charles IV of France died without a male heir. Queen Isabella made a claim to the throne of France on behalf of her son Edward, on the grounds that he was a matrilineal grandson of Philip IV of France. However, the precedents set by Philip V's succession over his niece Joan II of Navarre and Charles IV's succession over his nieces meant that the senior grandson of Philip III in the male line,