Just when our biggest banks thought they were out of the woods and into the money, the official consensus in their favor begins to crack. The Obama administration’s publicly stated view – from the highest level in the White House – remains that the banks cannot or should not be broken up. Their argument is that the big banks can be regulated into permanently low risk behavior.

In contrast, in an interview reported in the NYT this morning, Paul Volcker argues that attempts to regulate these banks will fail:

“The only viable solution, in the Volcker view, is to break up the giants. JPMorgan Chase would have to give up the trading operations acquired from Bear Stearns. Bank of America and Merrill Lynch would go back to being separate companies. Goldman Sachs could no longer be a bank holding company.”

Volcker may not have the ear of the President (as the NYT points out), and Alan Greenspan – also arguing for bank breakup, but along different lines – might also be ignored. But watch Mervyn King closely.

Mervyn King is governor of the Bank of England and a hugely influential figure in central banking circles. Time and again he has proved to be not only ahead of his peers in terms of thinking about the latest problems, but also the person who is best able to frame an issue and articulate potential solutions so as to draw support from other officials around the world.

Mervyn King also does not mince words. In a major speech last night, he said, “Never in the field of financial endeavour has so much money been owed by so few to so many. And, one might add, so far with little real reform.” (full speech)

He hits hard (implicitly) at the White House’s central idea on large banks: ”The belief that appropriate regulation can ensure that speculative activities do not result in failures is a delusion”. And he lines up very much with Paul Volcker’s views – breaking up big banks is necessary, doable, and actually essential.

Remember and repeat this Mervyn King line: “Anyone who proposed giving government guarantees to retail depositors and other creditors, and then suggested that such funding could be used to finance highly risky and speculative activities, would be thought rather unworldly. But that is where we now are.”

The big banks will push back, of course. But Mervyn King’s words mark the beginning of a new stage of real reform; the consensus starts to crack.

By Simon Johnson