One of the fond delusions of our age is that scientists are a breed apart from ordinary mortals, white-coated custodians of a mystery with authority to pronounce on any scientific issue, however remote it may be from their own field of expertise. A shining example was the status given to Sir David King, who has just retired after seven years as the government Chief Scientist. In 2001, when he was appointed by Tony Blair at the height of the foot-and-mouth crisis, Professor King’s speciality was ‘surface chemistry’. Yet immediately top of his agenda was the need to fight an animal disease.

The man he called in to tackle the epidemic was Professor Roy Anderson, a computer modeller specialising in the epidemiology of human diseases but without any experience in veterinary matters. Shutting their ears to the pleas of the world’s leading veterinary experts on foot-and-mouth that the only effective way to stop the spread of the epidemic was vaccination, the two men flouted the law by launching their ‘pre-emptive cull’, the mass-slaughter of animals which never had any contact with the disease. As many as eight million healthy animals were unnecessarily destroyed, at a colossal social and financial cost which vaccination might have reduced to a fraction.