Newcastle, William Cavendish, duke of, 1593?–1676, English soldier and politician. Of great wealth, Cavendish became (1638) governor of the prince of Wales and a privy councilor. During the civil war he supplied financial and military aid to the royalist cause, raising, maintaining, and leading troops in the northern counties. He was at first successful, but part of his force was defeated at Winceby by Oliver Cromwell in 1643, and after his defeat with Prince Rupert at Marston Moor in 1644 he retired to the Continent. He returned to England with Charles II at the Restoration, having expended nearly £1 million in the royalist cause. His estates were restored, and he was created duke of Newcastle in 1665. He engaged little in politics thereafter. Newcastle wrote several plays and books on horsemanship and was a lifelong patron of writers, among others Ben Jonson (who wrote two masques for the entertainment of Charles I at Newcastle's Welbeck estate in 1633 and 1634) and, later, John Dryden. His second wife, Margaret (Lucas) Cavendish, duchess of Newcastle, 1623?–1673, achieved contemporary notice for her poems, plays, essays, scientific treatises, letters, orations, and fantasies. Her biography of her husband (1667) was edited by C. H. Firth (1906).
See H. T. E. Perry, The First Duchess of Newcastle and Her Husband as Figures in Literary History (1918); D. Grant, Margaret the First (1957).