During 1142 and 1143, Geoffrey secured all of Normandy west and south of the Seine, and, on 14 January 1144, he crossed the Seine and entered Rouen. He assumed the title of Duke of Normandy in the summer of 1144. In 1144, he founded an Augustine priory at Chateau-l'Ermitage in Anjou. Geoffrey held the duchy until 1149, when he and Matilda conjointly ceded it to their son, Henry, which cession was formally ratified by King Louis VII of France the following year.