One thing we have learnt in the past year is that some banks are definitely too big to fail. We may yet discover something even more disturbing: that some are too big to save.

Tim Geithner, the US Treasury Secretary, who has staged something of a reputational recovery this week – helped by the fickle stock market – will this morning testify to Congress on his plans for reforming regulation and gaining more power to wind up insolvent financial institutions.

Mr Geithner has intelligent things to say about how the Treasury and the Federal Reserve could have done a better job of letting Lehman Brothers go down gracefully, and saving American International Group without having to stick to bonus contracts. He wants the US government to be able to seize control of such institutions when spending public money.