Mackenzie, John (1649?–1696?), presbyterian minister and historian, was born in 1647 or 1649 in the north of Ireland, possibly in Co. Down, though the family was also associated with a farm at Lowcross, near Cookstown, Co. Tyrone. He was educated at Edinburgh university, and graduated MA (1669); he was licensed to preach by Down presbytery, and in 1673 was ordained minister of Derryloran congregation, in Cookstown, Co. Tyrone. In 1688, with many others, he took refuge in the city of Derry just before it was besieged. Mackenzie was one of eight presbyterian ministers in the city, who preached regularly throughout the siege. He was asked by George Walker (qv) to be chaplain to Walker's regiment, which was largely composed of presbyterians; directly after the siege was lifted, Walker made a triumphal progress through Britain to London, where he published his account of the siege. His version of events did not please the presbyterians of Derry, and Mackenzie particularly objected to Walker's self-aggrandisement; the celebrity and rewards lavished on the Church of Ireland clergyman possibly also pointed up the contrasting circumstances that awaited Mackenzie in Cookstown, where his congregation could provide a stipend of £14 a year and a farm worth £8 or £9 a year. After reading Walker's account in December 1689, and without waiting for synod's sanction for his effort to put the presbyterian case, Mackenzie hurried to London in January 1690. There he collected documents and apparently canvassed support from officers who had served during the siege. He then published Narrative of the siege of Londonderry, or the late memorable transactions of that city faithfully represented to rectify the mistakes and supply the omissions of Mr Walker's account.
Mackenzie's work is a very useful alternative to Walker's account, and provides an intelligent perspective on events, as well as details that are missing in Walker; it is carefully organised, clearly written, and based at least partly on first-hand accounts and on documents which only Mackenzie preserved. However, its title, with its overt criticism of Walker, suggests that objective historiography was perhaps only accidentally achieved, and Mackenzie's undoubted significance as a pioneering historian is overshadowed by his role as defender of the presbyterian contribution to the protestant interest and to the survival of the city of Derry. As a result of his all too evident bias, later historians have been able to accuse him of unjustified and even malicious attacks on Walker. An anonymous friend of Walker (probably John Vesey (qv), archbishop of Tuam) replied to Mackenzie's volume in a 1690 pamphlet which ferociously criticised the Narrative as a ‘false libel’. Not to be outdone, Mackenzie replied in similar vein in another pamphlet the same year, Dr Walker's invisible champion foyl'd. . .. Walker's death at the battle of the Boyne in 1690 brought the first phase of the unseemly contention to a close, without the recourse to libel actions which would have further inflamed passions. The hostility between the two men and their two denominational traditions was still palpable in 1861, when James S. Reid (qv) published an edition of Mackenzie's Narrative, and it forms one of the dominant themes even in twentieth-century treatments of the siege and its significance in protestant folklore.
Mackenzie is said to have visited London in 1694 to seek an assurance from King William (qv) that presbyterians would be protected from prosecutions in church courts. Sources give two dates of death, 1696 and 1697, and there is no information about his wife or family, though he had descendants who still lived at Lowcross in the nineteenth century. He was buried in Derryloran graveyard.