Charles was allowed to keep his conquests of 1364, except for the citadel of Meulan, which was to be razed to the ground. In compensation Charles received Montpellier in Bas-Languedoc. His claim to Burgundy was to be referred to the arbitration of the Pope. The Pope never in fact pronounced on the matter. It was an ignominious end to Charles's 15 years of struggle to create a major territory for himself and his line in France. Henceforth he resided mainly in his kingdom. At the end of 1365 Séguin de Badefol arrived in Navarre to claim the considerable sums Charles had pledged to pay him for his services in Burgundy, even though he had achieved nothing of substance. Charles was not pleased to see him, received him in private and poisoned him with a crystallised pear. The cessation of war in France left vast numbers of French, English, Gascon and Navarrese soldiers and freebooters in search of mercenary employment, and many of these soon became involved in the wars of Castille and Aragon, both of which bordered Navarre. Charles typically tried to exploit the situation by making agreements with both sides that would enlarge his territory while leaving Navarre itself relatively untouched. Officially he was ally of Peter of Castile, but at the end of 1365 he concluded a secret agreement with Peter IV of Aragon to allow the marauding army led by Bertrand du Guesclin and Hugh Calveley invade Castile through southern Navarre in order to depose Pedro I and supplant him with his half-brother Henry of Trastámara. He then reneged on his agreements to both sides and attempted to hold the Navarrese borders intact, but was unable to do so and instead paid the invaders a large sum to keep their plundering to a minimum. After Henry of Trastámara successfully seized the throne of Castile, Pedro I fled to the court of the Black Prince in Aquitaine, who began to plot his restoration by sending an army across the Pyrenees. In July 1366 Charles himself came to Bordeaux to consult with Pedro I and the Prince and agreed to keep the mountain passes of Navarre open for the passage of the army, for which he would be rewarded with the Castilian provinces of Guipúzcoa and Álava as well as additional fortresses and a large cash payment. Then in December he met Henry of Trastámara on the Navarrese border and promised instead to hold the passes closed, in return for the border town of Logroño and more cash.