Scottish diplomat and author who was initially trained in law and medicine at the University of Edinburgh, though he never practised as a doctor. He had an interest in natural history and published on mineralogy of Scotland. During the Peninsular War he joined the army of Sir Arthur Wellesley (later Duke of Wellington), serving as an aide-de-camp (c. 1809-1812). He was elected a Fellow of the Linnean Society (1812), of the Geological Society of London (1813) and of the Roral Society (1815). MacKenzie travelled to Mexico with a British Commission (1823) and was appointed British Consul at Veracruz. He was later Consul-General in Haiti (1825-1830) and subsequently British Resident in Havana (1830), though he soon returned to England follwing the death of King George IV and did not return to Cuba until 1832. During his official travels he collected plants for several botanists including his friend W.J. Hooker, then at Glasgow but at K after 1841, and A.H.R. Grisebach (GOET). MacKenzie's employment with the Foreign Office was terminated following a dispute with H.J.T. Palmerston (1834) and he turned to literary and commercial interests. From 1846 he lived much of the time in the United States, particularly Boston and New York, where he died in a hotel fire in New York on 6th August 1862.