It says a lot about China’s size that a lender devoted to just one city can have $134bn in assets – even if that city is Shanghai. It says even more about China’s credit boom. In any case, Bank of Shanghai’s $90bn in customer deposits has appeal for Santander, which has just bought an 8 per cent stake in the Chinese lender from HSBC. Shanghai grannies’ savings will become more attractive if access to other forms of funding become constrained by a draft rule aimed at shrinking interbank credit markets, as bankers worry they will.

Investors in China, and particularly in Chinese banks, face a dilemma. In the long term, limiting credit growth – by reducing interbank lending, or by any other means – may avoid a devastating credit crisis. In the short term, investors want their lenders profitable and their borrowers liquid.

Can “Document No. 9”, as the draft rule is drably titled, solve the dilemma? A fifth of small-bank funding is interbank debt, double its share in 2010, Standard Chartered notes. Document No. 9 would stop banks lending out more than half of their deposit base to other banks, which sounds prudent.