He is in no doubt about the benefits. “It’s valid as long as it’s done properly. And it’s cost effective to the extent that it pays for itself—in three and a half years for a gastric bypass and 18 months for a band. It’s the most effective treatment for type 2 diabetes, with resolution of diabetes in over 80%, sometimes up to 98% of patients. And it’s permanent, unlike diet.” He accepts that there are risks: “1 in 300 don’t wake up. But risks can be managed—for example, by doing procedures in centres with a high level of anaesthetic expertise.”