Born 9th October 1727, was educated at Westminster school, and in 1744 went to Christ Church college, Oxford. He acquired a distinguished reputation as a scholar, and was the author of many eloquent Latin compositions. After succeeding to the title he spent some years on the continent, and in 1754 was chosen one of the sixteen Scots representative peers. The following year he was appointed ambassador extraordinary and pleni-potentiary to Vienna till 1772, when he was appointed in the same capacity to the court of France. In 1768 he had been made a knight of the Thistle. He remained in Paris till the commencement of hostilities in 1778, when he was appointed lord-justice-general of Scotland. On 27th October, 1779, he was constituted principal secretary of state for North Britain, an office which he held till the dissolution of Lord North's administration in 1782. On the formation of the coalition of the council, but on the rejection of Fox's India bill in December following, he resigned that office. He had married in 1759, at Warsaw, Henrietta Frederica, daughter of Henry, Count Bunau, councillor to the elector of Saxony, and by her had two daughters. That lady dying in 1766, he married, a second time, the Hon. Louisa Cathcart, third daughter of the ninth Lord Cathcart. On the death of the first, called the great earl of Mansfield, 20th March 1793, she succeeded as countess of Mansfield in the county of Nottingham, in her own right, the remainder having been to her, as the wife of his nephew, Viscount Stormont, under the impression prevalent at the period of the creation of the earldom, 31st October, 1776, that no British peerage could be limited to a peer of Scotland, even in remainder. When, however, the converse was established by law, the first earl of Mansfield obtained another patent, dated 26th July, 1792, creating him earl of Mansfield of Caen Wood, county Middlesex, with remainder to his nephew, her husband, Viscount Stormont. Accordingly, on the death of his uncle in 1793, he succeeded as second earl of Mansfield. On the division in the opposition 1794, he joined the administration, and on the 27th December that year was a second time appointed president of the council. He resigned the office of lord-justice-general in 1795. Besides the office mentioned, he also held those of joint clerk of the court of king's bench, and chancellor of Marischal College, Aberdeen. He died at Brighton, 1st September, 1796, in his 69th year, and was buried in Westminster Abbey in the same vault with the first earl of Mansfield.