Roger de Mortimer, deemed by some to have been son of William de Warren, and by others, of Walter de St. Martin, brother of that William, was founder of the abbey of St. Victor, in Normandy. "It is reported," says Dugdale, "that in the year 1054 (which was twelve years before the Norman Conquest), when Odo, brother of Henry, King of France, invaded the territory of Evreux, Duke William sent this Roger, then his general (with Robert, Earl of Ewe, and other stout soldiers), to resist his attempts; who meeting with Odo near to the castle of Mortimer, gave him battle, and obtained a glorious victory. It is further observable of this Roger that he was by consanguinity allied to the Norman duke (afterwards king, by the name of William the Conqueror), his mother being niece to Gunnora, wife of Richard, Duke of Normandy, great grandmother to the Conqueror." The presumed son of this Roger, Ralph de Mortimer, accompanying the Duke of Normandy in his expedition against England, was one of his principal commanders at the decisive battle of Hastings. [Sir Bernard Burke, Dormant, Abeyant, Forfeited and Extinct Peerages, Burke's Peerage Ltd, London, England, 1883, p. 382, Mortimer, Barons Mortimer, of Wigmore, Earls of March]