Campbell, Alexander, second Earl of Marchmont 1675-1740, was the eldest surviving son of Sir Patrick Hume of Polwarth, first earl of Marchmont, and his wife, Grizel, daughter of Sir Thomas Ker of Cavers. In his boyhood he shared his father's exile in Holland, with the other members of the family. He spent two or three years at the university of Utrecht, where he made a special study of civil law, being intended to follow the legal profession. On 25 July 1696 he was admitted to the Faculty of Advocates, and on 29 July 1697 married Margaret, daughter and heiress of Sir George Campbell of Cessnock, Ayrshire. He was afterwards knighted by the style of Sir Alexander Campbell of Cessnock. On 16 Oct. 1704 he was appointed an ordinary lord of session, in the place of Sir Colin Campbell, Lord Aberuchill, and took his seat on the bench on 7 Nov. as Lord Cessnock. In April 1706 he was returned as one of the members for Berwickshire, and accordingly sat in the last Scotch parliament which met for its final session in the following October. He zealously supported the union, and took an active share in the work of the sub-committee, to which the articles of the union were referred. In 1710 his eldest brother, Lord Polwarth, died, and in 1712 he went to Hanover, where he entered into correspondence with the electoral family, and was the means of contradicting the report which had been eagerly circulated, that the elector was indifferent to the succession to the English throne. In 1714 Campbell resigned his seat on the bench in favour of his younger brother, Sir Andrew Hume of Kimmerghame. He was made lord-lieutenant of Berwickshire in 1715, and at the breaking out of the rebellion raised four hundred of the Berwickshire militia in defence of the Hanoverian succession.
In the same year he was appointed ambassador to the court of Copenhagen, where he remained until the spring of 1721, and in December 1716 he received the further appointment of lord clerk register of Scotland. In January 1722 he was nominated one of the British ambassadors to the congress at Cambray. On the death of his father on 1 Aug. 1724 he succeeded to the earldom, and on 10 March in the following year was invested, at Cambray, by Lord Whitworth, with the order of the Thistle. In 1726 he was sworn a member of the English privy council, and in 1727 was elected one of the Scotch representative peers. In 1733, with other Scotch nobles, he joined in the opposition to Sir Robert Walpole's excise scheme in the hope that by joining forces with the English opposition Lord Islay's government of Scotland might be overthrown.
Though the bill was dropped, those who had opposed it were not forgotten by Walpole, and in May 1733 Marchmont was dismissed from his office of lord clerk register. In the following year he was not re-elected as a representative peer. He took an active part in the attempt to criminate the government for interference in the election of the Scotch peers, which, however, was not successful. He died in London on 27 Feb. 1740, in the sixty-fifth year of his age, and was buried on 17 March in the Canongate churchyard, Edinburgh. By his wife, Margaret, he had a family of four sons and four daughters. He was succeeded by his third son, Hugh [see Hume, Hugh, third and last Earl of Marchmont], through whose daughter, Lady Diana, the barony of Polwarth descended to her son, Hugh Scott of Harden.
Marchmont Papers, edited by Sir G. Rose (1831), vols. i. and ii.
Sir R. Douglas's Peerage of Scotland (1813), p. 182
Brunton and Haig's Senators of the College of Justice (1832), pp. 476, 477
Nicolas's Orders of Knighthood (1842), iii., T. 39, 41, 47, xxxii.
Scots Mag. 1740, ii. 94, 99-101
Foster's Scotch M.P.'s 45.
Contributor: G. F. R. B. [George Fisher Russell Barker]