Sir Richard Doll was the world's most distinguished medical epidemiologist. He established his reputation alongside Sir Austin Bradford Hill, showing that cigarette smoking caused lung cancer. He then went on to show it caused bladder and other cancers, and cardiovascular disease. He did seminal work with Richard Peto on the health of doctors and their families, demonstrating an increased incidence of suicide and liver disease. He also carried out major research on the risks and benefits of the contraceptive pill, on low level radiation, and the dietary treatment of gastric ulcers.

Doll went to work with Bradford Hill at the Medical Research Council in January 1948. Government statisticians had drawn the MRC's attention to a huge recent increase in lung cancer deaths, and the MRC held a conference to decide whether the increase was real and, if so, whether a cause could be identified.

At the time, said Doll, smoking seemed a normal and harmless habit. Eighty per cent of men smoked. Doll and Hill both thought the most likely cause would prove …