Born at Coburg, Ontario, Canada on 13 June 1869, fifth son of the Hon John Douglas Armour, Chief Justice of the Supreme Court of Ontario and his wife, *née* Clinch. He was educated at Upper Canada College and graduated with honours in natural science at the University of Toronto in 1891. He then came to England and took the MB degree at the University of London in 1894, the LRCP in 1896, the MRCP and MRCS in 1897. His first inclination therefore was towards the practice of medicine, but in 1900 he was elected FRCS and thereafter devoted himself to surgery. After returning for a short time to Toronto, he came back to England in November 1901 and was appointed an assistant demonstrator of anatomy at University College, London. Whilst working there he came under the influence of Victor Horsley, and through him was subsequently elected with Percy Sargent, FRCS surgeon to the National Hospital for Diseases of the Nervous System in Queen Square, Bloomsbury. On 20 April 1903 he was appointed assistant surgeon to the West London Hospital, where he was afterwards surgeon from 22 July 1912, and consulting surgeon from 25 April 1930, and dean of the West London Postgraduate School of Medicine from 28 October 1912. He was also surgeon to the Italian Hospital, to the Blackheath and Charlton Hospital and to the Acton Hospital. At the Royal College of Surgeons Armour was Arris and Gale lecturer in 1905, and in 1906 he won the Jacksonian prize with an essay on "The diagnosis and treatment of those diseases and morbid growths of the vertebral column, spinal cord, and canal, which are amenable to surgical operations". In 1908 he was a Hunterian professor of surgery and pathology. At the Medical Society of London he was Lettsomian lecturer in 1927, when he gave an accurate description of the modern surgery dealing with the spinal canal and its membranes. He was president in 1929 and was elected treasurer in 1932, a position he held at the time of his sudden death. He was also president of the West London Medico-chirurgical Society in 1928, of the neurological section of the Royal Society of Medicine in 1928-29, and of the Association of British Neurological Surgeons 1930-32. He was also an active member of the British Medical Association, being a member of the representative body at Belfast in 1909 and in London in 1910. At the Sheffield meeting in 1908 he was secretary of the section of surgery, in 1910 secretary of the section of medical sociology, and in 1914 vice-president of the section of neurology and psychological medicine. For many years Armour was medical officer to King Edward's Horse (The King's Oversea Dominions Regiment), and when war began in 1914 he was attached as a surgical specialist to several military hospitals with the rank of lieutenant-colonel, his commission being dated 7 September 1914. Most of his work was done at the Canadian hospital supported by the Imperial Order of the Daughters of the Empire, and for these services he was created CMG in 1918. He married Louise, daughter of Captain Ormsby McKnight Mitchell of the US Army, who survived him with a son and two daughters. One of his brothers became a judge of the Canadian Senate Court. He died suddenly and without previous warning at a meeting of the council of the Medical Society of London on 23 October 1933. Armour was a man of abounding energy and masterful personality. Of a big frame, with rugged and strong features, his face was marked by a long oblique scar running across his right cheek. His voice was stentorian and he spoke with a Canadian accent. Not an easy man with whom to work, he retained many of the characteristics of individuality and resourcefulness which must have led his ancestors to leave their native country and act as pioneers. His general surgical work was good but not outstanding, and as a neurological surgeon he relied somewhat too much on the use of complicated mechanical appliances. Publications: The surgery of the spinal cord and its membranes (Hunterian lectures). *Lancet*, 1908, 1, 693, etc. The surgery of the spinal cord and its membranes (Lettsomian lectures). *Ibid*. 1927, 1, 423, etc. The surgery of the posterior cranial fossa. *Ibid*. 1932, 2, 499. The operation of gastro-duodenostomy. *Brit med J*. 1905, 1, 122.