A doctor does not stop a sick patient’s medicine just because they have been taking it for six months. It is similarly inconceivable that the Federal Reserve would turn off its emergency lending facility for investment banks while their access to credit is still very much crunched. That has consequences, however: there can no longer be any prospect of a return to regulatory “business as usual” on Wall Street.

Ben Bernanke, Fed chairman, has given a strong steer that the central bank will continue to allow broker-dealers such as Goldman Sachs and Merrill Lynch to borrow at its discount window after mid-September. That facility means that the brokers can be all but certain of borrowing overnight at only 25 basis points above the Fed’s main interest rate; in turn, the knowledge that such a fail-safe exists is an inducement for private investors to lend to the investment banks.