A week after scrambling to handle a discharge of tonnes of poisonous metals into a local river on which millions rely for drinking water, Jiang Yimin, the chief of the environment protection bureau in Hunan, south-central China, was adamant. Further spillages would be prevented, he vowed to visitors.

In Mr Jiang’s sights were 50 to 60 small factories producing indium, a metallic element used in the manufacture of semi-conductors and liquid-crystal display screens, near the Xiang river, about an hour by road from the provincial capital, Changsha. “I am signing the order to close them today!” he declared.