Gilbert de Clare, 5th Earl of Hertford, who, after the decease of Geoffrey de Mandeville, Earl of Essex, the 2nd wife of Isabel, the divorced wife of King John, and in her right Earl of Gloucester, and her own decease, s. p., as also the decease of Almarick D'Evereux, son of the Earl of Evereux by Mabell, the other co-heiress, who likewise succeeded to the Earldom of Gloucester, became Earl of Gloucester, in right of his mother, Amicia, the other co-heiress. This nobleman was amongst the principal barons who took up arms against King John, and was appointed one of the twenty-five chosen to enforce the observance of Magna Carta. In the ensuing reign, still opposing the arbitrary proceedings of the crown, he fought on the side of the barons at Lincoln, and was taken prisoner there by William Marshall, Earl of Pembroke; but he soon afterwards made his peace. His lordship m. Isabel (who m. after his decease, Richard, Earl of Cornwall, brother of King Henry III), one of the daus., and eventually co-heiress of William Mareschal, Earl of Pembroke, by whom he had issue, Richard, his successor; William; Amicia, m. to Baldwin de Redvers, 4th Earl of Devon; Agnes; Isabel, m. to Robert de Brus. The earl d. in 1229 and was s. by his eldest son, Richard de Clare. [Sir Bernard Burke, Dormant and Extinct Peerages, Burke's Peerage, London, 1883, p. 119, Clare, Lords of Clare, Earls of Hertford, Earls of Gloucester]