Jackman, Isaac (c.1740–1831), newspaper editor and playwright, was born in Dublin, son of a clerk in the office of the lord mayor; nothing more is known of his family. He qualified as an attorney at King's Inns in 1762 and practised in Dublin for some years before departing for London. There he married a wealthy woman; but at her death, which occurred soon after the marriage, her annuity stopped. Jackman, left penniless, turned to writing for the stage. His first work was the comic opera ‘Milesian’, which opened at Drury Lane on 20 March 1777 and was indifferently received. The following month he had much greater success with his farce ‘All the world's a stage’, which opened at Drury Lane on 7 April 1777 and was frequently revived. After this success Jackman seems to have taken over the editorship of the Morning Post, formerly an opposition paper, which was bought by the government in 1776. As the identities of the editors were kept secret it is difficult to ascertain dates for Jackman's tenure, but in November 1780 the paper was involved in a scandal engineered by Henry Bate, proprietor of the rival Morning Herald, and this resulted in Jackman challenging Bate's emissary to a duel and his name being in the public arena. Shortly after this he appears to have been dismissed, but he may have returned subsequently; the DNB puts him as a likely candidate for one of the two Irishmen who edited the Morning Post between 1786 and 1795. According to the Dublin University Magazine, he was also editor of an Irish paper after 1780.
Jackman wrote four more plays. ‘The divorce’, a farce, was produced at Drury Lane on 10 November 1781 and was moderately well received. ‘The man of parts; or, A trip to London’ was another farce, judged by the Dublin University Magazine to be the worst of his plays. It was acted in Crow St. Theatre in Dublin and was published in 1785. Two years later the classical burlesque ‘Hero and Leander’ appeared at the Royalty Theatre, Goodman's Fields, and had a good run. ‘Almirina’ also appeared at the Royalty and was a one-man play, acted by John Palmer with the aid of wooden and pasteboard figures. This idea did not originate with Jackman but had been put into practice by Samuel Foote in his ‘Tragedy-a-la-mode’. After 1787 Jackman wrote no further plays and nothing further is recorded of him until his death in 1831.