The words flashed on the screen and changed his life.

Edwin Hardeman had struggled through six rounds of chemotherapy in 2015 when he saw a TV report that said exposure to a popular weedkiller could lead to the exact cancer that was destroying his life. For the first time, the Californian had a possible explanation for his disease.

What he didn’t know then was that four years later, he would become the first person to prove in US federal court that Roundup had caused his non-Hodgkin lymphoma (NHL) – and that in the process, he would help uncover damning secrets about the manufacturer, Monsanto, and its influence in science and government.

“I hope this is a significant turnaround in Monsanto’s history,” Hardeman, 70, said on a recent morning in his Windsor living room, his first interview since a jury ruled that the company was liable for his cancer and owed him $80m in damages. “Maybe they will finally do the right thing.”