Sir Richard Doll is widely acknowledged as the father of modern cancer epidemiology; a title that is well merited by his output of high quality research over more than five decades. His work led to our understanding of the preventable environmental causes of cancer, the most notable of which was a case control study that established the link between smoking and lung cancer. Moreover, his study answered the objections of skeptical and critical colleagues and provided the definitive evidence. In this he identified a truth that the world has yet to come to terms with completely, but one that continues to influence governments and people internationally and that has lead to the saving of millions of lives throughout the world.

By establishing a long-term follow-up cohort study of the health of British doctors, he was able to identify additional risk factors of smoking for other cancers and for heart disease. He has also shown, after 40 years, that half of those who continued to smoke died as a result of their habit, but that those who gave up smoking reverted to their pre-smoking risk.

Doll's second major contribution, and the one that is reported as having given him most pleasure, was his demonstration of the linear dose-response relationship between ionising radiation and leukaemia. In this he showed that there is no absolutely safe dose of radiation. Previously, it was thought that cancer was produced only by large doses sufficient to cause macroscopic damage to tissues and it was the repair process that caused the cancer.

Widening his field of research, he pioneered studies into the effects of exposure to asbestos, coal gas and nickel refining processes. And this lead to his establishment of the Cancer in Five Continents series in which with collaborators, he provided the first well documented evidence of the proportions of cancer that could be attributed to specific causes such as smoking, nutrition, infection, occupational and environmental exposure. His work has an enormous world-wide influence on preventive initiatives for cancer.

Doll has continued to publish major papers on oral contraceptive and hormone replacement therapy and their associated cancer risks. He has called attention to the risks of passive smoking and to diet including alcohol consumption in promoting cancer, cardiovascular disease and other conditions.

Although he retired as Regius Professor of Medicine in 1979, he continues to publish both papers and contributions to books and to give fascinating and highly topical talks and lectures. Currently, he is working on the 50-year follow-up to his original cohort study.

Sir Richard Doll's work has been highly influential both in its results and its methods. With his collaborators he successfully promoted the use of numerical methods in medicine, in the design of clinical trials as well as in epidemiology. The British Medical Journal said of him in 1997 " More than anybody else Sir Richard Doll has stopped doctors pontificating without any evidence"