The consultant cardiac surgeon at Papworth looks at the development of tools to measure how well surgeons and hospitals are performing. He addresses the crucial decisions faced by anyone contemplating a medical intervention: should I keep taking the tablets? Should I have an operation? Which surgeon should I choose? He reveals why requesting a surgeon with the lowest patient mortality rate could be a mistake; how anaesthetists seem to make no difference to the outcome of an operation, but surgeons do; and why patients operated on the day before a surgeon goes on holiday are twice as likely to die as those operated on during that surgeon’s first day back.