“Give me a lever and somewhere to stand,” boasted Archimedes, “and I will move the world”. Give bankers too much leverage (and somewhere to hide), financial regulators appear to have concluded, and they may very well blow the whole thing up.

Hence the leverage ratio. This stipulates that a bank's assets - regardless of how risky they are perceived to be - must be backed up by a strict minimum amount of equity. Advocates of the measure say it is the simplest way to rein in the wilder tendencies of the banks. But if they think that the leverage ratio can't be gamed, they should think again.