[q. v.] as solicitor-general in Pitt's administration (London Gazettes, No. 12534). He received the honour of knighthood on 27 June 1788, and on the following day was appointed attorney-general (ib. 1788, p. 313). In December 1789 Macdonald prosecuted John Stockdale for a libel on the House of Commons (Howell, State Trials, xxii. 237–308), and in December 1792 Thomas Paine for publishing the ‘Rights of Man’ (ib. pp. 357–472).
Meantime, at a by-election in February 1777, he was returned to the House of Commons for the borough of Hindon in Wiltshire. His first reported speech in the house was delivered on 4 Dec. 1778 in defence of the manifesto issued by the American commissioners (Parl. Hist. xix. 1391–3). During the debate on the Earl of Upper Ossory's motion respecting the state of Ireland, on 6 Dec. 1779, Macdonald ‘made one of the severest attacks upon the minister [Lord North], in his personal character, that was ever known in a House of Parliament,’ accusing him ‘of being a poor, pitiful, sneaking, snivelling, abject creature, fraught with deceit, and one whom no man of honour could support or trust as a minister or an individual’ (ib. xx. 1228); he subsequently apologised for these ‘hasty expressions’ (ib. p. 1241).
At the general election in September 1780 Macdonald was returned for Newcastle-under-Lyme, and continued to represent that borough until his elevation to the judicial bench. In February 1781 he opposed Burke's bill for the regulation of the civil list establishments (ib. xxi. 1269–70), and, in May 1782, Pitt's motion for parliamentary reform (ib. xxii. 1429). During the debate on Coke's motion for the appointment of an administration entitled to the confidence of the people in March 1783, Macdonald made a violent attack upon the newly formed coalition, which elicited a spirited reply from Fox (ib. xxiii. 672–6). In the following November Macdonald opposed the second reading of Fox's East India Bill (ib. pp. 1297–1301). On 23 June 1785 he moved for leave to bring in a bill for the better securing the peace of the cities of London and Westminster and the borough of Southwark, by which he proposed that ‘a total reformation should be made in the regulation of the police’ (ib. xxv. 888–94), but owing to the opposition of the corporation he was unable to carry it through the house. He appears to have spoken for the last time in parliament on 17 Dec. 1792 (ib. xxx. 131–2). In February 1793 he was appointed lord chief baron of the exchequer in the place of Sir James Eyre [q. v.], and on the 12th of that month took his seat on the bench for the first time, having previously been sworn in as a serjeant-at-law. On the 15th he was admitted a member of the privy council (London Gazettes, 1793, pp. 126, 127, and Anstruther, Reports, 1796, i. 172). Macdonald was one of the judges who took part in the trial of Thomas Hardy in 1794 (Howell, State Trials, xxiv. 199–1408), and he presided at the trial of Governor Wall at the Old Bailey in January 1802 (ib. xxviii. 51–178). After serving twenty years on the bench, Macdonald retired with a pension in November 1813, and was created a baronet on the 27th of that month. He died at his house in Duke Street, Westminster, on 18 May 1826, aged 79, and was buried in Kensington Parish Church.
Macdonald was a lineal descendant of the old Lords of the Isles. His ancestor Donald Macdonald of Sleat was created a baronet of Nova Scotia on 14 July 1625, with a special clause of precedency, which placed him second of that order in the kingdom of Scotland. Macdonald's eldest brother, James, who succeeded as the eighth baronet, was known as ‘the Scottish Marcellus.’ He was one of the most accomplished scholars of the day, and died at Rome on 26 July 1766, aged 24 (London Gazettes, 1766, No. 10653). His other brother, Alexander, succeeded James as the ninth baronet, and on 17 July 1776 was created Baron Macdonald in the peerage of Ireland.
Macdonald was distinguished neither as a lawyer nor as a parliamentary speaker, and owed his successful career mainly to a fortunate marriage. Though possessing a hasty temper he made a careful and impartial judge. He was for many years a well-known figure in society, where his conversational talents and agreeable manners made him a great favourite. According to Sir Gilbert Eliot, afterwards Lord Minto, Jekyll gave Macdonald ‘the nickname of the Arabian knight for having a thousand and one tales’ (Life and Letters of the first Earl of Minto, 1874, ii. 413). Macdonald became a bencher of Lincoln's Inn in Hilary term 1778, and acted as treasurer of that society in 1789.
He married, on 26 Dec. 1777, Lady Louisa Leveson-Gower, the eldest daughter of Granville, second earl Gower, afterwards first marquis of Stafford, by his second wife, Lady Louisa Egerton, daughter of Scroope, first duke of Bridgewater. There were seven children of the marriage, viz.: (1) James, who succeeded to the baronetcy; (2) Francis, who entered the royal navy, and died on 28 June 1804; (3) Caroline Margaret, who, born on 26 Nov. 1778, died young; (4) Susan, who, born in 1780, died unmarried at Lisbon
