Frederica Susanna Mildmay, Countess FitzWalter, 3rd Countess of Mértola was a British peeress.
Frederica, Countess FitzWalter (circle of Joseph Highmore, 1727)
Robert Darcy, 4th Earl of Holderness,, known before 1721 as Lord Darcy and Conyers, was a British diplomat and politician who served as Secretary of State for the Northern Department from 1754 to 1761
Frederica Mildmay, Countess of Mértola
…daughter of Charles I Louis, Elector Palatine. On 26 May 1715, she married Robert Darcy, 3rd Earl of Holderness, and they had two surviving children: Hon. Robert Darcy (1718–1778); later 4th Earl of Holderness. Lady Caroline Darcy (d. 1778); who married William Kerr, 4th Marquess of Lothian…
Joshua Reynolds Robert d’Arcy, 4th Earl of Holderness Google Art Project
George II at the Battle of Dettingen by John Wootton, 1743. Holderness is shown with George II and the Duke of Cumberland