Born on 7 January 1879 the son of William John Harnett FRCP Ed, LRCSI, of Barnet, Hertfordshire, he was educated at the City of London School and was a scholar of St John's College, Cambridge, where he took first-class honours in the Natural Sciences Tripos, part I, 1899. He entered St Thomas's Hospital with a university scholarship, and served as house surgeon, demonstrator of morbid anatomy, and assistant pathologist. At Netley he won the Montefiore prize and passed second of his year into the Indian Medical Service on 2 February 1907. He was promoted Captain three years later and in 1911 was transferred from military duties to be civil surgeon at Gauhati, and then at Kamrup, Assam. In 1914 he was appointed resident surgeon of the Calcutta Medical College and surgeon to HE the Governor of Bengal, but during the war of 1914-18 he served on the North-West Frontier, in hospital ships, and at Salonika. He was promoted Major on 2 August 1918, and given hospital duty at Constantinople and in the Black Sea area. He returned to India in 1925 as Superintendent of Campbell Medical School, Calcutta, was promoted Lieutenant-Colonel on 2 August 1926, and returned as professor of surgery to the Calcutta Medical College in 1930. He had taken his MD at Cambridge in 1929. Harnett was an excellent teacher, as well as a first-class surgeon particularly interested in orthopaedics. He was created CIE in 1933 and retired in 1934. He was President of the Calcutta branch of the British Medical Association in 1934. Settling in London Harnett began a new career as an active member of many professional committees, especially those organised by the British Medical Association, and as a statistician researching for the British Empire Cancer Campaign. He was medical secretary of the Campaign's clinical cancer research committee 1938-51, and between 1942 and 1950 published a series of invaluable papers on statistical aspects of cancer in the Campaign's *Annual Reports*. He summarised his results in an important volume: *A survey of cancer in London*, 1952. During the war of 1939-45 he was an extra member of the India Office medical board. He married in 1909 Nellie Bartingale who survived him, but without children. Harnett died suddenly on 24 April 1957, aged 78, while attending the funeral of Sir George Cockerill, with whom he had served in India, at Golders Green. He was a simple, unassuming man, meticulously accurate, and always ready to help his juniors. Publications: Histological study of human parathyroid glands. *Trans Path Soc* 1907, 58, 128-154. Differential blood count in dengue. *Ind med Gaz* 1913, 48, 45-49.