The immediate cause of Philip's conflict with Richard the Lionheart stemmed from Richard's decision to break his betrothal with Philip's sister Alys at Messina in 1191. Some of Alys's dowry that had been given over to Richard during their engagement was part of the territory of Vexin. This should have reverted to Philip upon the end of the betrothal, but Philip, to prevent the collapse of the Crusade, agreed that this territory was to remain in Richard's hands and would be inherited by his male descendants. Should Richard die without an heir, the territory would return to Philip, and if Philip died without an heir, those lands would be considered a part of Normandy.