Geoffrey de Mandeville, 1st Earl of Essex to the crown, perhaps in part due to a large fine levied by Henry I due to his displeasure at the escape of an important political prisoner when William was in charge of the Tower of London. The King also held the substantial estate of Geoffrey's maternal grandfather Eudo "le Dapifer" to which Geoffrey laid claim. Geoffrey gained Eudo's lands and his father's offices during the shifting tides of fortunes of the two competitors for the English throne after King Henry I's death in 1135. He initially supported Stephen, who sometime in 1140 (most likely May of that year) made
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