Paul Volcker, the former chairman of the Federal Reserve, is almost as renowned as his successor Alan Greenspan for talking in code, once rebuffing rumours that the Fed had intervened in the currency markets with the response: “We did what we did, we didn’t do what we didn’t do, and the results were what happened.”

The contrast with the clear message sent out by the rule that bears his name, which will force banks to reduce if not shed their proprietary trading activities, could not be clearer.