|SOME NOTES ON MEDIEVAL ENGLISH GENEALOGY|
Volume 3, page 246, note b:
He [Gilbert de Clare (d. 1307), son of Thomas de Clare, lord of Thomond] m. Isabel. ... His widow was living 20 Apr. 1322.
Douglas Richardson, in August 2002, posted evidence that Isabel was in 1312 the wife of John de Hastings, knight, lord of Bergavenny [citing Canterbury and York Society, vol. 41, pp. 778, 779 (1934)]. Thus she was the daughter of Hugh (le Despenser), Earl of Winchester, by Isabel, daughter of William (de Beauchamp), Earl of Warwick. She later married Ralph de Monthermer (d. 1325) [Complete Peerage, vol. 6, p. 348; vol. 9, p. 142].