By Martin Webber
Editor BBC World Service business news
How tightly will Wall Street banks be regulated in the future?
Will an 82-year-old veteran central banker be the man who finally stops the music for the bankers of Wall Street?
A Congressional hearing in Washington on Tuesday may well provide the answer.
A week ago, US President Barack Obama, appeared to be telling America that the ideas of Economic Recovery Advisory Board chairman Paul Volcker would be the centrepiece of his plan to make the global financial system safer, announcing that the "Volcker rule" would determine the future of the world's banks.
But since then, there has been complete confusion as to exactly what the President and Mr Volcker have in mind.
Since the start of the financial crisis, the consensus among the leading nations has been that in future regulators need to take a careful look at the risks banks take and make sure what they do is safe.
The problem with this proposal is that it is exactly the way the system was set up up in the run-up to the crisis.
Regulators in the UK and US convinced most people in the boom years that they were keeping a careful eye on all the risks.
When President Obama toughened his stance against the banks a week ago, he said the "Volcker rule" would mean banks could not operate hedge funds, private equity or get involved in proprietary trading "unrelated to client needs".
Proprietary trading is anything where the bank holds a financial asset with its own cash and therefore bears the risk of trading losses. The plan sounded pretty radical.
The BBC has obtained a recent article by Mr Volcker for a specialist magazine, OMFIF (Official Monetary and Financial Institutions Forum).
In it, Mr Volcker made it clear that he wants a complete separation of commercial banks from the financial markets.
"We simply cannot afford further financial market breakdowns," said Mr Volcker's article.
"I favour a separation of commercial banking activities that are essential to the functioning of our financial system from more speculative trading-oriented capital markets activities that are not.
"To lower the risk and vulnerability of commercial banks, I favour prohibiting their ownership or sponsorship of hedge funds, private equity funds, and large-scale purely proprietary trading activities in securities, derivatives or commodity markets.
"These measures would directly eliminate potential areas of risk, reduce conflicts of interest and focus management attention on the core functions of banking."
Like oil and water
Mr Volker was seen as a hugely successful and independent chairman of the Federal Reserve under United States Presidents Jimmy Carter and Ronald Reagan, from August 1979 to August 1987.
His ideas are strongly supported by many people who follow retail banking, who feel the reckless property related-lending that led to the crisis was a result of the swashbuckling culture of Wall Street investment bankers that now control finance.
"The investment bankers had effectively achieved something extraordinary in a period of as little as 20 years - control over many of the largest retail deposit-taking institutions in the world," says Michael Lafferty, chairman of Lafferty Group, a global banking research house.
"My personal view is that retail banking and investment banking are like oil and water - and will never really mix.
"We have at last the opportunity to return banking to real bankers, concerned about customers and with a proper appreciation of risk, and to help markets break out of their extreme tendency for booms and busts of the past three decades."
Mr Volcker's ideas appear to have won the backing of Mervyn King, governor of the Bank of England.
"The most important thing is that we are prepared to countenance major reform," says Mr King.
"Unless we actually think about the deep structural issues that have led us to where we are, we'd be doomed to go through it again, but on a larger scale."
But for those who think that there are signs that something radical may actually come out of this crisis, there is one fairly major unresolved issue, namely Treasury Secretary Timothy Geithner - the man in charge of President Obama's economic policies.
In an aside to his testimony to Congress on AIG, Mr Geithner went out of his way to praise the contribution to the US economy of Wall Street banks.
While Mr Geithner said he fully supported the "Volcker rule", he went on to outline what he thought it meant - and a clear separation of banking for ordinary people and Wall Street trading was not how he explained it.
For Mr Geithner, the "reform" model that he wanted pushed through Congress amounted simply to "limiting" banks from taking too much risk.
"You should be subjected to a set of constraints on capital, on leverage and how you are funded that limit the amount of risks you take," said Mr Geithner.
"If in addition to that you want to own a bank and operate a bank, then there are a set of other limits that we think are good and in the public interest so you cannot take advantage of that access to the safety net (government guarantees) to subsidise a set of activities that are not essential."
So will banks such as Citigroup in America and UK-based Barclays be broken up?
It seems likely on Mr Volcker's version of the Volcker rule, but not under Mr Geithner's vision, which seems to be all about regulation of the current structure, but with greater care.
The investment bankers are already warning that bank lending and future economic growth could fall unless the banks are protected from the huge uncertainty arising from the announcement of the "Volcker rule".
A large share of profits at Goldman Sachs come from proprietary trading.
They are the world's leaders in clever trades that take calculated bets on market movements.
One would therefore have thought that the "Volker rule" would imply that Goldman Sachs could no longer be a bank.
Yet Mr Geithner's testimony appeared to suggest that he did not want Goldman to cast off its recently won status as a bank holding company with direct access to government funds.
Markets simply do not know what to think. They hope they will be better informed after Tuesday.