1325, she returned to France, initially as a delegate of the King charged with negotiating a peace treaty between the two nations. However, her presence in France became a focal point for the many nobles opposed to Edward's reign. Isabella gathered an army to oppose Edward, in alliance with Roger Mortimer, 1st Earl of March, whom she may have taken as a lover. Isabella and Mortimer returned to England with a mercenary army, seizing the country in a lightning campaign. The Despensers were executed and Edward was forced to abdicate—his eventual fate and possible murder remains a matter of considerable historical debate. Isabella ruled as regent until 1330, when her son, Edward deposed Mortimer in turn and ruled directly in his own right. Tensions in Gascony, 1323–1325 Isabella's husband Edward, as the Duke of Aquitaine, owed homage to the King of France for his lands in Gascony. Isabella's three brothers each had only short reigns, and Edward had successfully avoided paying homage to Louis X, and had paid homage to Philip V only under great pressure. Once Charles IV took up the throne, Edward had attempted to avoid doing so again, increasing tensions between the two. One of the elements in the disputes was the border province of Agenais, part of Gascony and in turn part of Aquitaine. Tensions had risen in November 1323 after the construction of a bastide, a type of fortified town, in Saint-Sardos, part of the Agenais, by a French vassal. Gascon forces destroyed the bastide, and in turn Charles attacked the English-held Montpezat: the assault was unsuccessful, but in the subsequent War of Saint-Sardos Isabella's uncle, Charles of Valois, successfully wrested Aquitaine from English control; by 1324, Charles had declared Edward's lands forfeit and had occupied the whole of Aquitaine apart from the coastal areas. Edward was still unwilling to travel to France to give homage; the situation in England was febrile; there had been an assassination plot against Edward and Hugh Despenser in 1324—the famous magician John of Nottingham had been hired to kill the pair using necromancy—and criminal gangs were occupying much of the country. Edward was deeply concerned that should he leave England, even for a short while, the barons would take the chance to rise up and take their revenge on the Despensers. Charles sent a message through Pope John XXII to Edward, suggesting that he was willing to reverse the