It’s not easy to get hold of Ángel Hernández, the legendary Mexican chemist who for a decade provided illicit performance-enhancing drugs to numerous athletes, including, he claims, all eight 100 metres finalists at the Beijing Olympics. It took me just over a year of trying. The FBI also struggled. The story goes that when they eventually caught up with him in 2005 he had been holed up in a hotel room in Texas, living under an assumed name for two years.