Infuriating as it must be for head teachers to be informed by pupils selling contraband sweets: “We were just doing what you taught us in business studies,” the kids have a point. For in these days of schools purged of vending machines and chips, the gap in the market was ripe for exploitation by junior moguls.

Let us consider Jamie Oliver, who spearheaded the campaign for enforced healthy eating in schools. Oliver is a credit to the nation in two fields. One is eating, but do not forget that the other is entrepreneurship. As a child, Oliver never received pocket money, but he could always afford the right trainers. How? By converting a couple of lockers into an underground tuck shop and selling sweets. Even as his prodigious talent in the kitchen grew, his sideline in strawberry laces from his illicit sweeteasy waxed fat with profit. In later life, he has seen no irreconcilable contradiction in extolling the virtues of home-grown greens and accepting plenteous greenbacks from Sainsbury's for endorsing its supermarkets. With such a role model, it is hard to blame teenagers who have seen among their sugar-starved peers potential customers.

Besides this, however bad the obesity crisis, however upsetting the prevalence of diabetes, news that children are selling junk food in the playground provokes an intuitive response: better E-numbers than Ecstasy tablets. If banning cheeseburgers and fruit pastilles in schools lends to a quarter of cola cubes the illicit thrill the average teenager may previously have sought from more immediately damaging and unlawful sources, then bravo for this black market.