However, Eustace switched sides in 1212 (the biography puts it down to Eustace's enemy Renaud de Dammartin allying himself with John and poisoning John's mind against Eustace) and raided Folkestone when English troops seized his Channel Island bases. When civil war broke out in England in 1215, he supported the rebel barons and ferried Prince Louis of France across the Channel to help them in 1216.