Louis-Marie-Florent de Lomont d'Haraucourt, marquis later duc du Châtelet (20 November 1727, Semur-en-Auxois – 13 December 1793, Paris), was an aristocratic French Army general and diplomat of the Ancien Régime. The Duke served as Governor of Semur-en-Auxois in Burgundy as well as Ambassador to the Court of St James's, besides other appointments. He was appointed to command the Regiment of French Guards shortly before the outbreak of the Revolution in 1789. Châtelet was subsequently imprisoned and guillotined, in 1793 aged 66. Family The son and heir of the noble and ancient Châtelet family, his mother, Émilie du Châtelet, famously was a scientist and the lover of Voltaire. On 20 June 1725, his father Florent-Claude du Chastelet married Gabrielle-Émilie, daughter of Louis Nicolas le Tonnelier de Breteuil. Like many marriages among the French nobility, theirs was an arranged marriage. The couple found they had little in common, but proprieties were observed in accordance with contemporary norms. The Marquis and Marchioness produced three children: Françoise-Gabrielle-Pauline (30 June 1726 – 1754, married in 1743 to Alfonso Carafa, Duca di Montenero), Louis-Marie-Florent (later duc du Châtelet, November 20, 1727 - guillotined on 13 December 1793) and Victor-Esprit (born on 11 April 1733 and died on 29 August 1734). After bearing three children, Émilie, Marquise (Marchioness) du Châtelet, considered her marital responsibilities fulfilled and reached an agreement with her husband to live separate lives while still maintaining one household. Marriage The Duke of Châtelet married, in 1752, Diane-Adélaïde de Rochechouart (died 1794) but they had no children. The Duke adopted his wife’s niece instead, also called Diane-Adélaïde, who was daughter of François-Jacques de Damas, marquis d'Antigny. She was born in Paris on 25 January 1761. Having married, in 1777, Charles-François, comte de Simiane, thereby becoming styled Countess by courtesy, it soon became apparent that she had married a homosexual. Thereafter she sought comfort elsewhere with Gilbert du Motier, marquis de La Fayette who had served in the American Revolutionary War together with her husband (François, comte de Simiane died on 27 March 1787). The Duke also had an affair with her for the decade prior to his death in 1793. She never remarried and spent the remainder of her years at Chateau de Cirey, until her death (April 9, 1835). Political role In 1787 Châtelet was appointed to preside over the provincial assembly of the Ile-de-France, one of a number called to consider political and