This spring, a curious type of underground banking is proliferating in parts of China. Called minjian jeidai, it enables Chinese companies to borrow short-term money from wealthy households, rather than banks, via a broker armed with a mobile phone.

On paper, the practice seems almost logical. Many small and medium-sized companies in China are currently finding it hard to get loans from banks; and many Chinese households desperately need somewhere to put their money (other than the overheated property sector or falling stock market).

But there is a catch. Since the practice is illegal, lending rates are very high; moreover nobody knows how large this practice might be. In the City of Qingdao, which I happened to visit yesterday, for example, some bankers and officials “guessed” that minjian jeidai accounts for more than 10 per cent of local finance, a huge sum. “But nobody really knows,” one official hastily added, officially, this practice does not even exist.