research he discovered the possibility of using the radioactive isotope cobalt-60 to treat cancer. In 1946, he returned to England and became Professor of Radiotherapeutics at the University of Cambridge. He was also appointed Director of the Radiotherapeutic Centre at Addenbrooke's Hospital. During this appointment he became internationally known for his work on the treatment of cancer by irradiation. In 1957, he was appointed Regius Professor of Physic, succeeding Sir Lionel Whitby. In 1958, he gave the Dunham Lectures at Harvard University. He oversaw the expansion of medical teaching at Cambridge, including the introduction of two new chairs; Professor of Medicine in 1963 and Professor of Surgery in 1965. He also oversaw the development of the new School of Clinical Medicine. In 1975, he stepped down from the Regius Professorship and returned to his previous appointment of Professor of Radiotherapeutics. He retired from academia and clinical medicine in 1976. Personal life In 1934, Mitchell married Lilian Mary Buxton who was eight years his senior. together they had two children; a son and a daughter. His wife predeceased him in 1983 but he was survived by his children. In retirement he continued to live in Cambridge in a house on Huntingdon Road. He died on 22 February 1987 in Cambridge. Honours In 1952, Mitchell was elected a Fellow of the Royal Society (FRS). He was elected a Fellow of the Faculty of Radiologists (FFR) in 1954 and a Fellow of the Royal College of Physicians (FRCP) in 1958. In 1975, when the Faculty of Radiologists became a Royal College, he became a Fellow of the Royal College of Radiologists (FRCR). In the 1951 King's Birthday Honours, he was appointed Commander of the Order of the British Empire (CBE). In 1967, he was awarded the Pirogoff medal by the USSR Academy of Sciences. References 1909 births 1987 deaths Regius Professors of Physic (Cambridge) People from Birmingham, West Midlands People educated at King Edward's School, Birmingham Alumni of the University of Birmingham Alumni of St John's College, Cambridge Fellows of St John's College, Cambridge Fellows of the Royal Society Fellows of the Royal College of Physicians Commanders of the Order of the British Empire British radiologists 20th-century British medical doctors