Geoffrey de Mandeville (which surname he assumed), who, in the 15th King John (1314-15), had livery of the lands of his inheritance and the same year, bearing the title of Earl of Essex, the king gave him to wife, Isabel, Countess of Gloucester, 3rd dau. and co-heir of William, Earl of Gloucester, and was, in her right, Earl of Gloucester, and was so styled in the convention with King John, 1215 (which Isabel had first been m. to King John himself, but repudiated on account of consanguinity). This nobleman afterwards distinguished himself amongst the barons who rebelled again the tyrannical power of John, and was one of the twenty-five lords chosen to enforce the observance of Magna Carta, about which period, attending a tournament at London, he received a wound from a lance, which proved mortal. His lordship d. in 1216, and leaving no children, was s. by his brother, William. [Sir Bernard Burke, Dormant, Abeyant, Forfeited and Extinct Peerages, Burke's Peerage, Ltd., London, England, 1883, p. 353, Mandeville, Earls of Essex]