William of Ypres to the English throne following Henry I's death in 1135 finally changed William's fortunes for the better. He commanded Stephen's troops against the forces of their cousin, Henry's daughter Empress Matilda, who claimed the throne. Many of the soldiers were William's fellow Flemings, including his brother. Stephen's campaign in Normandy failed because the local noblemen refused to co-operate with William and other Flemings. William was much more active in England, where he took part in the Battle of Lincoln (1141), during which Stephen was captured by the Empress's forces. William led his contingent away when it became clear that the
Henry I of England now had the best claim to the throne. William of Breteuil championed the rights of Robert, who was still abroad, returning from the Crusade, and to whom Henry and the barons had given homage in previous years. Henry argued that, unlike Robert, he had been born to a reigning king and queen, thereby giving him a claim under the right of porphyrogeniture. Tempers flared, but Henry, supported by Henry de Beaumont and Robert of Meulan, held sway and persuaded the barons to follow him. He occupied Winchester Castle and seized the royal treasury. Henry was hastily crowned king in Westminster