MacNally, Leonard (1752?–1820), barrister, writer, United Irishman, and informer, was born in Dublin, the only son of William MacNally (d. 1756), a grocer. It seems that his mother brought him up with the support of his uncle, a merchant named Featherstone of St Mary's Lane. A contemporary who knew him well, John O'Keeffe (qv), recollected that he had ‘such a passion for private plays that he was indulged in having a little theatre fitted up in his mother's house’. If he was baptised a catholic, he later conformed to the established protestant church. He is presumed to have been the Leonard MacNally who had a brief career as a grocer in St Mary's Lane, Dublin, ending in bankruptcy (September 1772).
MacNally entered the Middle Temple in London to study law on 8 June 1774. His call to the Irish bar (1776) not proving lucrative, he returned to London and earned a living by writing for the press and the stage. At some stage he edited the Public Ledger, a morning newspaper. Influenced by Laurence Sterne (qv), he published a travel narrative, Sentimental excursions to Windsor and other places (1781). Of his dozen or so plays the earliest was The apotheosis of Punch (1779). His first real success was Retaliation, or, The citizen a soldier (1782), performed at the Theatre Royal, Covent Garden; the next was Tristram Shandy, a sentimental Shandean bagatelle (1783); his greatest was Robin Hood, or, Sherwood Forest, a comic opera (1784). MacNally's earliest known political statements were articles on Ireland in the European Magazine (April–August 1782) and a pamphlet, The claims of Ireland and the resolutions of the Volunteers vindicated (1782), that brought him to the attention of Fox, for whom he acted in the Westminster election (1782). His belated call to the English bar (30 May 1784) seems to have brought him some legal work, for he wrote only four more plays, the last an opera, The cottage festival (1796).
In or before 1790 he returned to Dublin, resumed practice at the Irish bar, and published An address to the Whig Club with an essay on the judicial discretion of judges (1790). By December 1791 he was a member of the Dublin Society of United Irishmen (formed 9 November), after which he attended its meetings regularly, often speaking; he was a member of the committee appointed to draw up plans for parliamentary reform (11 January 1793); he fought a duel (29 April 1793) with Sir Jonah Barrington (qv), who had spoken ill of the society's members; and he was present at its final meeting (23 May 1794).
Six weeks before the society was dissolved a French spy, William Jackson (qv), whose purpose was to ascertain support in Ireland for a French invasion, arrived in Dublin and dined with MacNally, who had known him in London. MacNally facilitated meetings with Archibald Hamilton Rowan (qv), James Reynolds (qv), and Theobald Wolfe Tone (qv). Jackson's companion, a London attorney, John Cockayne (also known to MacNally in London), proved to be an informer; consequently Jackson faced charges of high treason (which cost him his life), Rowan and Reynolds fled, and Tone emigrated. It is likely that MacNally, confronted with evidence of his complicity with Jackson, was induced to turn informer. Probably from the summer of 1794, certainly no later than April 1795, he was giving information to John Pollock (qv), who passed it on to the under-secretary at Dublin Castle, Edward Cooke (qv). MacNally was defence counsel in several important trials for treason, most notably those of Jackson himself, Laurence O'Connor (qv), the brothers John Sheares (qv) and Henry Sheares (qv), and Robert Emmet (qv). It was MacNally who first gave reliable information to Dublin Castle on Tone's having removed from America to France and been with the French military expedition to Bantry Bay. He was Dublin Castle's ‘most reliable and consistent source of information on United Irish developments’ (Elliott, 73). His perfidy and turpitude in betraying the defence strategies and confidences of clients, though it was suspected in 1811 by Daniel O'Connell (qv), was not fully revealed until the publication by R. R. Madden (qv) of the second edition of his United Irishmen (1858). He was not even well remunerated for his services until he was granted a pension of £300 p.a. (June 1801). MacNally was the author of The rules of evidence on pleas of the crown (1802) and The justice of the peace for Ireland (1808). An English barrister, Sir John Carr, who visited the Four Courts in 1805, found that MacNally was ‘regarded as an able criminal lawyer’. Probably he lost more than he gained from his association with radical politicians and their betrayal. He was not appointed a judge.
In the 1790s Leonard MacNally lived at 57 Dominick Street; in 1800 he moved to 22 Harcourt Street, which was where, at the age of sixty-seven or sixty-eight, he died on 13 or 15 February 1820. He was buried at Donnybrook. MacNally married three times, firstly in the early 1780s. Of his first wife nothing is known other than that she died on 27 March 1786. His second wife, Frances Janson of Richmond, Yorkshire, he immortalised in his ballad, with music by James Hook, ‘The lass of Richmond Hill’; she died in 1795. He married in May 1799 Louisa, daughter of the Rev. Robert Edgeworth of Issaid, Co. Longford; with her he had at least three sons, two of whom, John (b. 1803?) and Robert, went in for the law. Louisa MacNally was the author of a novel, revised by her husband before its publication, Eccentricity (1820). A Dublin attorney, Leonard Howard, a member of the Dublin Society of United Irishmen, is listed by Keane as a son of MacNally by Mary O'Brien. A portrait of Leonard MacNally is printed by Madden. Though he had a poor physique, ‘he had a handsome expressive countenance and alive sparkling eyes’ (O'Keeffe).