1154 Roger "filius Episcopi" assumed the name Mortimer after the battle of Mortemer against Odo, brother of King Henry I of France, in which Roger took the castle of Mortemer in Seine-Maritime.
Research Notes:
Roger's father has been identified as Hugh, bishop of Coutances, and his mother as a niece of Gunnor, Duchess of Normandy (wife of Richard I of Normandy).