When Roche received large orders for Xenical, its prescription-only slimming medicine, from the operator of a chain of private diet clinics in 2002, suspicions were raised among staff.

Robin Huxley was soon accounting for most of Xenical's UK sales outside the NHS. Questions were asked inside Roche about how he could be attracting so many patients. But in the next three years, the pharmaceutical company offered him discounts and even direct financial support.