 Determined to secure a claim for his family, he sent his chancellor, Thomas Becket, to press for a marriage between Margaret and Henry's heir, Henry the Young King.Louis agreed to this proposal, and by the Treaty of Gisors (1158) betrothed the young pair, giving as a dowry the Norman city of Gisors and the surrounding county of Vexin.Louis VII was devastated when Constance died in childbirth on 4 October 1160.