William Cavendish, 5th Duke of Devonshire (1748-1811), Lord High Treasurer of Ireland

Sitter in 7 portraits
The 5th Duke is best known for his first wife Georgiana, Duchess of Devonshire. He came from one of the wealthiest and most powerful Whig families, but was neither particularly ambitious nor particularly able. He was married twice: first, to Lady Georgiana Spencer; and subsequently to Lady Elizabeth Foster, nee Hervey, daughter of the 4th Earl of Bristol, who had been his mistress and his first wife's friend and confidante in a ménage à trois for more than twenty years. He served as Lord Treasurer of Ireland from 1764 until 1793.