Smithers trained initially in radiology and became a pioneer of the new speciality of radiotherapy. He was appointed to the London University Chair of Radiotherapy at the Institute of Cancer Research in 1943, and in the same year became Director of the Radiotherapy Department at the Royal Marsden Hospital. He soon realised the potential medical uses of the new developments in physics, especially the production of artificial radioactive isotopes and high-energy X-ray beams.
With the medical physicist Val Mayneord he conceived the idea of a new centre for the application of nuclear physics to medicine. Frustrated by the inadequacy of the Royal Marsden site in Chelsea for his purposes, and the failure to purchase an adjacent site, David Smithers and his colleagues were instrumental in the acquisition of the grounds of the Downs Hospital, in Sutton, Surrey, where the new hospital was to be built. He worked tirelessly as Chairman of the Building Committee, and eventually the Surrey branch of the Royal Marsden Hospital was opened by the Queen in 1963.
Smithers's intention was that the hospital and its associated Institute of Cancer Research should eventually be sited entirely at Sutton, but many of his colleagues were opposed to moving so far from the centre of London. Nevertheless the success of the Surrey branch over the subsequent decades more than vindicated his vision. He built up research in both radiotherapy and radiobiology and his unit acquired an international reputation for training young clinicians and scientists from many countries. In collaboration with the cancer professor Gordon Hamilton-Fairley and experts of several other countries, he played a leading part in the advances which led to a spectacular increase in the cure rates of testicular cancer and Hodgkin's disease.
As a clinical scientist he concurred with the Austrian philosopher Karl Popper in the view that a theory must be testable by experiments designed to prove it false. He stressed in many writings that cancer is a disorder of organisation of the human body, rather than a defect of cells. In a controversial article in the Lancet in 1962 entitled "Cancer - an Attack on Cytologism", he castigated the concept of cancer as a disease in which people are devoured by their own cells gone wrong, and criticised much of the cancer research of the time as based on this false premiss and lacking direction, thereby gaining the opprobrium of many in his own institute. He did, however, appreciate the irony that the improvements in treatment with which he was associated were achieved largely by the destruction of cancer cells using radiation and the non- specific cell poisons of which he philosophically disapproved, while the simultaneous efforts in cancer immunology yielded very little fruit.
It was, however, much more as a clinician than as a scientist that Smithers excelled. He set an outstanding example to generations of young doctors passing through his unit in how to relate to patients as people. He stressed the importance of reading the case notes thoroughly before meeting the patient and insisted on having a photograph of the patient in the notes to remind him of the personal details; in this way he was always able immediately to gain the patient's confidence. This sensitive approach was linked with meticulous attention to the details of the treatment. He would tell his students more about his pleasure in the recovery and long life of individual patients than about the statistical results of his treatments.
David Smithers delighted in his family, his home and his beautiful garden in Knockholt, in Kent, where he grew roses and entertained his staff. His tea parties, when he took great pleasure in showing visitors his roses, accompanied by croquet on the lawn, provided his overseas visitors with a quintessential memory of England.
After retirement in 1974 he began a new career as an author. He wrote on a number of subjects mainly with a literary flavour, including Jane Austen, Dickens and his beloved Kent. In This Idle Trade (1989), a book written mainly about doctors as authors, he stressed the importance of a broadly based humanist education for recruits to the medical profession, and expressed his concerns about the danger that the modern intensive training of doctors may produce too narrow a specialist who is not able to take a broad view.
When he gained a richly deserved knighthood in 1969 he followed his father and grandfather as the third in successive generations of his family to be so recognised for public services.
J. M. Henk
David Waldron Smithers, radiotherapist: born 17 January 1908; Professor of Radiotherapy, London University 1943-73 (Emeritus); Director, Radiotherapy Department, Royal Marsden Hospital 1943-73; President, British Institute of Radiology 1946-47, Faculty of Radiologists 1959- 61; Kt 1969; married 1933 Gwladys Angel (died 1992; one son, one daughter); died 20 July 1995.