John's position in France was considerably strengthened by the victory at Mirebeau, but John's treatment of his new prisoners and of his ally, <answer>William de Roches</answer>, quickly undermined these gains. De Roches was a powerful Anjou noble, but John largely ignored him, causing considerable offence, whilst the king kept the rebel leaders in such bad conditions that twenty-two of them died. At this time most of the regional nobility were closely linked through kinship, and this behaviour towards their relatives was regarded as unacceptable. <answer>William de Roches</answer> and other of John's regional allies in Anjou and Brittany deserted him in favour of Philip, and Brittany rose in fresh revolt. John's financial situation was tenuous: once factors such as the comparative military costs of materiel and soldiers were taken into account, Philip enjoyed a considerable, although not overwhelming, advantage of resources over John.[nb 6]
Who deserted John in favor of Philip?
William de Roches