| Constituency | Dates |
|---|---|
| Aberdeenshire | 1747 – 1754 |
| Elgin Burghs | 1 Jan. 1755 – 28 Jan. 1771 |
Under-sec. for Scotland 1742 – 46; commissary in Brussels for negotiating a commercial agreement with Austria and the Netherlands 1752 – 55; envoy to Prussia 1756 – June 1765, Dec. 1765 – d.
Mitchell’s father, a rich and eminent divine, five times moderator of the General Assembly, married him at the age of 14 to an heiress aged 10. After the deaths of his wife, sister, father, and infant daughter, he left Scotland in 1730, possessed of a substantial fortune, to continue his studies abroad. Returning home in 1735, he was made private secretary to Lord Tweeddale, on whose appointment to be secretary of state for Scotland in 1742 Mitchell became under-secretary till Tweeddale’s resignation in 1746.
In 1747 Mitchell accepted an offer by his relation, Sir Arthur Forbes, M.P. for Aberdeenshire, to stand down in his favour.
I have seen [he wrote] so much of the management of parties and known too many Members to think of the House of Commons as I once did ... The promises of great men are lighter than air ... I have hopes of the Duke of Newcastle and his brother’s concurrence but ... everything is to be feared from a certain eminent personage [the Duke of Argyll] who does not choose that his countrymen should be known to or connected with anybody but himself ... I am resolved to act a fair and honourable part if ever I shall be in Parliament, but I do propose a reward for myself—that of being employed either at home or abroad in a station agreeable to me and in which I may be useful; for my ambition at present is stronger than my avarice.1Culloden Pprs. 475-7.
He was returned, with the support of the Pelhams, at whose instance Argyll also declared for him.2Argyll to Pelham, 12 Aug. 1747, Newcastle (Clumber) mss. Pressed to declare that he owed his election to Argyll, he refused,3Mitchell to Newcastle, 15 July 1747, Add. 32712, f. 121. thus incurring the Duke’s displeasure. He also made himself unpopular with his compatriots by defending General Philip Anstruther.4Walpole, Mems. Geo. II, i. 95. But his real crime, he was told, was
in having some share of the Duke of Newcastle’s and Mr. Pelham’s favour, without depending upon those who call themselves the Scotch ministry.5HMC 5th Rep. 627.
Owing to Argyll’s hostility he was forced to give up his seat in 1754, but in 1755 Newcastle persuaded Argyll to let him in for Elgin Burghs. Next year he was appointed envoy to Berlin, where he died 28 Jan. 1771.