Born in Hampstead on 6 June 1882 the son of William James Walker, he was educated at the Leys School and Caius College, Cambridge, where he took first-class honours in the Natural Science Tripos in 1904. He had his clinical training at St Bartholomew's Hospital, where he was assistant editor of the Journal and President of the Abernethian Society. He qualified with the Conjoint Diploma in 1906, graduated in medicine and surgery at Cambridge in 1907, and took the Fellowship in 1908, after serving as demonstrator of physiology and house physician at St Bartholomew's. He won the Jacksonian Prize in 1910 with his essay on *Tumours of the bladder and male genitalia*, having decided to specialise in genito-urinary surgery, and was lecturer in venereal diseases at Bart's Medical College. He was a Hunterian Professor in 1911 and again in 1922 and 1924. Between 1920 and 1913 he worked in Argentina as resident surgeon at the British Hospital in Buenos Aires, and retained happy and vivid memories of his South American experiences. During the first world war he served in the RAMC in France, was mentioned in despatches three times, and became surgeon to the Duchess of Westminster's War Hospital. On demobilization he was appointed urological surgeon to the Royal Northern Hospital, which he served for more than twenty years, retiring at the age limit of 65 in 1947. He was also a consulting surgeon at St Bartholomew's. He was active in many surgical societies, including the Surgery and Urology Sections of the Royal Society of Medicine and the Venereal Diseases Section of the British Medical Association, and for many years was medical secretary of the British Social Biology Council. Walker made a distinguished contribution to his specialty as surgeon, writer and teacher. He endeared himself to his students by his complete freedom from pomposity, and to his colleagues by his gaiety and wit; a friend wrote that "his laugh was always an appreciation, not a sneer." He had many interests and friends outside medicine. He enjoyed fox-hunting, and in his middle years regularly played tennis in Regent's Park. He became more and more interested in the personal and social problems of medical practice both for the doctor and the patient. He was a fluent talker and writer, and in later years a prolific author on the mystical background of life and on psychological and spiritual suffering. He also wrote books for children, three or four popular medical books such as *Physiology of sex and its social implications* (1940), several volumes of reminiscences and a history of medicine in the 1950's, and during his last twenty years at least a dozen books expressing his mystical interpretation of life. His thought was profoundly influenced by his friendship with the Russian religious emigrés P D Ouspensky and G I Gurdjieff. He was a handsome man, but quite careless of appearance, and his character combined innocence with experience. Walker married twice; in 1926 Eileen Marjorie Wilson, and in 1944 Mary Piggott. He died at Midhurst on 22 January 1966 aged 83, survived by the son and daughter of his first marriage. Publications: *Diseases of the male organs of generation*. 1923. *The enlarged prostate*. 1926, and 2nd edition 1933. *Sex difficulties in the male*. 1934. *Genito-urinary surgery*, by Sir John Thomson-Walker, 2nd edition by K.W. 1936. *Human sterility and impaired fertility* (with C L Roberts and others). 1939. *Sexual disorders in the male* (with E B Strauss). 1944.