The British epidemiologist Sir Richard Doll failed to disclose that he was in the pay of a chemical company for 20 years while he was investigating links between a company product and cancer, The Guardian reported today.

The company, Monsanto, was paying Sir Richard $1,500 a day, according to a contract found among his papers in the Wellcome Foundation library. That contract, dated April 29, 1986, extended an agreement that began in May 1979. While on Monsanto’s payroll, Sir Richard told an Australian commission that there was no evidence that one of Monsanto’s products, the defoliant known as Agent Orange, caused cancer, the British newspaper reported. Agent Orange was widely used by American forces in the Vietnam War, and lawsuits against its manufacturer persisted for many years after the conflict ended.

Sir Richard, who died last year, was famous for his work in helping to demonstrate that smoking causes lung cancer.