Born at Pontefract on 12 September 1904, the son of a general practitioner, George Blomfield was educated at Malvern and Trinity College, Cambridge, where he graduated with first-class honours in the mechanical sciences tripos. Despite his gift for mathematics and mechanical science he was, after three years as a marine engineer in Sunderland, attracted to medicine, which he studied at Leeds, and graduated MB, ChB in 1933, taking the Conjoint diploma in the same year. Obstetrics and gynaecology were his first care, and he filled a number of posts including that of tutor in obstetrics (1936-40) at Leeds. Radiotherapy interested him and, after a period as director of the radium department in Leeds General Infirmary, he succeeded Frank Ellis in 1943 as medical director of the Sheffield National Centre for Radiotherapy. He chose to concentrate his interests and exploit his special clinical background, and from this emerged the "Sheffield" system of treatment of carcinoma of the cervix, and of the bladder. In 1957-58 he was vice-president of the Faculty of Radiologists; he had been on the Council of the British Institute of Radiology, and in 1963 became president of the Sheffield Medico-Chirurgical Society. He was lecturer in radiotherapy at the University of Sheffield, and a member of the Cancer and Radiotherapy Advisory Committee of the Central Health Services Council. His recreations were skiing, skating, swimming, and mountain climbing, and he held a glider-pilot's certificate. Photography, astronomy, and painting were also among his interests. George Blomfield married Mary daughter of William Gough, professor of obstetrics at Leeds. They lived at 29 Taptonville Road, Sheffield; he died in the Royal Hospital, after a short illness, on 5 July 1964, aged 59, survived by his wife, four sons and a daughter.