Elizabeth Christiana Cavendish, Duchess of Devonshire, society hostess and patron of the arts, was born Elizabeth Hervey in 1757 at Horringer, Suffolk. Her parents were Frederick Augustus Hervey, 4th Earl of Bristol (1730-1803), and Elizabeth Davers (1730-1800). She was known for most her life as Lady Elizabeth Foster, Bess to her friends.
She spent her formative years in semi-poverty abroad and in Ireland, where her father was the Bishop of Derry. In 1776, she married John Thomas Foster (b. 1747), with whom she had two sons, Frederick (b. 1777) and Augustus (b. 1780). The marriage was an unhappy one and the couple separated in 1780; Foster retained custody of their sons, and did not allow the boys to see their mother for 14 years.
In 1782, while lodging with her aunt in Bath, she met William Cavendish, 5th Duke of Devonshire, and his wife Georgiana. After only a few weeks of acquaintance she moved in with them. There was much speculation about the nature of their relationship. Foster certainly became mistress of the 5th Duke, and the closest friend and confidante of Duchess Georgiana.
In December 1784 she became pregnant with the Duke's child. Using her health as a pretext, she went to Naples and gave birth in secret to Caroline Rosalie on 16 August 1785. Subsequently travelling to Provence in France, she persuaded the elderly Comte St Jules to accept paternity of Caroline, and returned to Britain in July 1876.
She gave birth to a second child, Augustus Clifford, in France on 26 May 1788. There was some doubt about whether the Duke of Devonshire was the father of this child as Foster was also having an affair at this time with Charles Lennox, 8th Duke of Richmond.
In 1790, Bess succeeded in having her children brought from France to live in the nursery with the three legitimate Cavendish children.
She accompanied the Duchess of Devonshire in her exile to the continent in the early 1790s, where the Duchess gave birth to Eliza Courtney, her child by Charles Grey, in 1792.
The Duchess died in 1806, making Foster her executrix and sole guardian of her papers. To the outrage of all, Foster married the Duke of Devonshire on 19 October 1809. She was widowed a mere two years later and began living by herself in Piccadilly Terrace, London. Styling herself Elizabeth, D uchess of Devonshire, she entertained in a regal manner and made several new friends, including Lord Byron.
In 1816 Duchess Elizabeth moved permanently to Rome and began a new career as a liberal patron of the arts, and of archaeologists in particular. Her final years were spent in the company of Cardinal Hercule Consalvi, secretary of state to the Vatican, who shared her passion for the arts. She funded the excavation of the Forum for 11 years, and the city of Rome recognized her efforts with a medal struck in her honour. She died in Rome on 30 March 1824, and her body was interred in the Cavendish vault in Derby Cathedral.
Elizabeth Foster was a witness and participant in Whig politics between 1784 and 1809 and, as Elizabeth Cavendish, an active patron of Rome's classical heritage between 1813 and 1824. Her diaries, although rewritten several times, provide valuable insight into the period. An acknowledged beauty, she was irresistible to a variety of men and women. She was frequently labelled artificial and duplicitous, but she retained the love and trust of Georgiana, duchess of Devonshire, for twenty-five years, and afterwards the unceasing companionship of Cardinal Consalvi.
Principal source: Amanda Foreman, 'Cavendish [née Hervey; other married name Foster], Elizabeth Christiana, duchess of Devonshire (1757-1824)', Oxford Dictionary of National Biography (Oxford: Oxford University Press, 2004). By permission of Oxford University Press.