Born on 7 February 1870 son of Thomas Lyle MA, TCD an official in the Board of Education, and his wife née Webb, he was educated at King's College School, London, and proceeded to King's College and its Hospital, which was then still in Clare Market near the College. He won many scholarships and prizes, was demonstrator of physiology and lecturer in animal biology, and house surgeon in 1894. His interest in ophthalmology was aroused by M M McHardy, but at first he was more interested in physiology and in 1895 was appointed senior assistant to Professor W D Halliburton. He was for a time tutor and senior demonstrator in anatomy at Sheffield Medical School, but was appointed in 1900 lecturer in biology and zoology and in 1904 lecturer in physiology at King's College, London. He examined in biology for the Conjoint Board in 1901-03, in physiology for the Fellowship in 1911 and 1917-19, and for the DOM, when it was founded in 1921. He also taught biology at the Birkbeck Institution, and wrote a *Manual of Physiology* (1911) which was popular with medical students for more than twenty years, running into three editions. He was a brilliant coach. At King's College Hospital he served as ophthalmic assistant, was elected to the honorary staff in 1910, becoming ophthalmic surgeon and lecturer in ophthalmology in 1917, and consulting surgeon in 1930 when he retired. He was from 1903 on the staff of the Royal Eye and Royal Ear Hospitals; at the Royal Eye Hospital he started the teaching and served as Dean. Lyle identified himself with the work of King's College Hospital Medical School, where he was Dean from 1911 to 1931. He was given the title of Emeritus when he retired, the only Dean of the School thus honoured. He compiled a detailed biographical history of the school in 1935, adding an addendum fifteen years later. He was a member of the Physiological and Ophthalmological Societies, and was elected a Fellow of King's College, London in 1922. Lyle married four times: (1) in 1896 Mary Deacon, who died in 1897 leaving a daughter; (2) in 1901 Elizabeth Selfe, who died in 1905 leaving two sons, Thomas Keith Selfe Lyle FRCS and Eric H W Lyle MD both ophthalmologists, and a daughter; (3) in 1909 Anne Winton, widow of Dr Thompson Playfair, who died in 1919 leaving a daughter; (4) in 1924 Grace Kime, who survived him but died on 20 December 1957; all his children survived him. Lyle was an original member (1889) of the King's College Hospital Association Football Club. He lived at Bromley, Kent, and was consulting ophthalmic surgeon to the Bromley and Beckenham Cottage Hospital. He retired to Portishead, Somerset, where he died on 13 March 1956 aged 86. A memorial service was held in King's College Hospital Chapel on 28 March. Publications: *The Eyesight of children attending elementary schools*. 1897. Abnormal conditions of the circulatory system of the frog. *J Physiol* 1899, 24, p vi. Veratrine-like action of glycerine on muscle. *J Physiol*. 1901, 26, p xxvi. Effect of tobacco on the eyes. *Practitioner* 1905, 75, 68. *A Manual of Physiology*. Oxford 1911; 2nd edition, with D de Souza, 1921; 3rd edition, 1930. *King's and some King's men*. Oxford 1935, 613 pages; *An addendum* ... 1950, 211 pages. *Applied physiology of the eye* completed and edited by T K Lyle, Bailliere 1958.