A Tesco supermarket in a suburb of Shanghai announced two weeks ago it would sell 3,000 bottles of cooking oil at half price. Hundreds queued and when the doors opened, there was a stampede. Nineteen people, most of them housewives, needed hospital treatment.

The cooking oil incident was one of several that have broken out across China in recent weeks. In the most serious, three people were trampled to death at the weekend in the western city of Chongqing after a Carrefour store offered a 20 per cent discount on five-litre bottles of rapeseed oil.