Robert Darcy, 4th Earl of Holderness

Robert Darcy, 4th Earl of Holderness, (17 May 1718 – 16 May 1778), known before 1721 as Lord Darcy and Conyers, was a British diplomat and politician.
Career.
In 1741 he collaborated with G.F. Handel in the production of Deidamia. From 1744 to 1746 he was ambassador at Venice and from 1749 to 1751 he represented his country at The Hague. In 1751 he became Secretary of State for the Southern Department, transferring in 1754 to the Northern Department, and he remained in office until March 1761, when he was dismissed by King George III in favour of Lord Bute, although he had largely been a cipher in that position to the stronger personalities of his colleagues, successively the Duke of Newcastle, Thomas Robinson, Henry Fox, and William Pitt the Elder. From 1771 to 1776 he acted as governor to two of the King's sons, a solemn phantom as Horace Walpole calls him. He left no sons who survived childhood, and all his titles became extinct except the Baronies of Darcy de Knayth and Conyers, which were baronies by writ inherited from his father, and the Portuguese countship of Mértola, inherited from his mother. In those peerages he was succeeded by his daughter, Amelia Osborne, Marchioness of Carmarthen.
David Hume wrote, "It is remarkable that this family of d'Arcy [sic] seems to be the only male descendant of any of the Conqueror's barons now remaining among the Peers. Lord Holdernessae [sic] is the heir of that family".
Family.
He was the only surviving son of Robert Darcy, 3rd Earl of Holderness, and his wife Lady Frederica Schomberg. On 29 October 1743, Darcy married Mary Doublet, daughter of Francis Doublet and Constantia Van-der-Beck. The couple had three children, only one of whom survived childhood: