Margaret de Newburg, 7th Countess of Warwick
Margaret de Newburg, 7th Countess of Warwick or Margaret de Beaumont (died 3 June 1253), was the daughter of Henry de Beaumont, 5th Earl of Warwick and Margaret D'Oili. She was the sister and heiress of Thomas de Beaumont, 6th Earl of Warwick, and became the 7th Countess of Warwick in her own right. She married first John Marshal, and secondly, John de Plessis. The latter was a great favourite of King Henry III of England, who in 1247, created him the 7th Earl of Warwick and subsequently, Count of Warwick. He died on 20 February 1263. There was no issue by either of these marriages, and so at Margaret's death, the estates passed to her cousin, William Maudit, who became the 8th Earl.
- Lee, Sidney, ed. (1896). "Plessis, John de". Dictionary of National Biography. 45. London: Smith, Elder & Co.
|Peerage of England|
Thomas de Beaumont
| Countess of Warwick