John McArthur was born in Doncaster in 1911 and was one of three brothers who trained at Guy's Hospital. He graduated in 1934 and after several resident appointments at Guy's, including a house surgeon job with Sir Heneage Ogilvie, he decided on a career in surgery after demonstrating physiology. At the outbreak of war he spent some five years in the RAF medical branch attached to Bomber Command, returning to Guy's as a surgical registrar. He then served as a senior surgical registrar at Chester where he met his wife, Pauline, an anaesthetist. A long-standing interest in neoplastic disease attracted him back to the department of radiotherapy at Guy's, a small unit under the directorship of Carter Braine. From a senior registrarship there he moved to Newcastle as consultant radiotherapist in 1953 and, on the death of Carter Braine in the following year, he was appointed assistant surgeon to the radiotherapy department at Guy's. He also became consultant radiotherapist to Pembury Hospital in Kent and later held appointments at Farnborough Hospital and West Hill Hospital, Dartford. Following his succession as consultant radiotherapist at Guy's he remained there until his retirement in 1976 with emeritus status. John McArthur harnessed his skills as an experienced clinician and general surgeon to the discipline of radiotherapy. Together with Tony Wayte he helped to plan a new radiotherapy department at Guy's which was opened in 1960, and a year later this included one of the first linear accelerators in the country. He collaborated well with his colleagues in allied disciplines, gave forthright and clear statements of policy and maintained high standards of training. He was never keen to give formal lectures and preferred to devote himself to the service of his patients who appreciated his compassionate and commonsense approach. Together with Philip Reading, then consultant ENT surgeon to Guy's, he set up one of the first multidisciplinary clinics to review patients with head-and-neck malignancies. He had a very happy family life in Blackheath with many friends. He was interested in gardening, antiques and sport (especially cricket) and was justly proud of his villa and garden in Portugal. He died of malignant disease on 11 June 1981, after a long illness, born with dignity and courage, and was survived by his wife, son John, also an anaesthetist, and daughter Anne, a physician.