LONDON BRIEFING:THE "Cleggmania" that has swept the UK – or at least its chattering classes – since last week's historic televised debate between the three main party leaders is putting Liberal Democrat economic policies under renewed scrutiny in the City of London.

Nick Clegg, judged by to have “won” the debate by a wide margin, is storming ahead in opinion polls, forcing many to reassess his party’s chances on May 6th.

Winning a debate and winning an election are, of course, entirely different things but Britain’s third party is being taken more seriously now than ever seemed possible.

Even the bookies have been forced to rip up their odds. A bet on the Lib Dems gaining an overall majority is still a long shot at 20-1 but that compares with 300-1 before the debate.

And punters can get 12-1 on Clegg becoming prime minister or 7-1 on him being home secretary.

So swift a shortening of the odds is, say the bookies, unprecedented.

As for a hung parliament, they now judge that to be odds-on.

Back in the real world, the Lib Dem election manifesto is being re-read more attentively than when it was launched on the eve of the debate.

Like Labour and the Conservatives, the Lib Dems have provided only sketchy details of how they plan to tackle the “elephant in the room” – Britain’s debt mountain.

Nick Clegg’s party has, however, furnished voters with more manifesto commitments on its tax and spending plans than either of the two main parties.

More detail on their economic agenda was provided this week, as the new golden boy of British politics pledged to reinvent the banking system, breaking up the “too-big-to-fail” super-banks and, in the process, ensuring that the lending taps are turned back on and that the risk-takers are not rewarded with any more taxpayers’ money.

Dismissing the Tories as the “party of choice” for greedy bankers and again accusing Labour of having been asleep at the wheel when the banking crisis struck, Clegg reminded us that he has some personal experience in this area – his father, Nicholas, was a banker.

Clegg Sr was a director of Hill Samuel and co-chairman of Daiwa Europe, and also served as a senior adviser to the Bank of England on banking supervision.

That was in a bygone era, but not all bankers are greedy, Clegg said.

“Old-fashioned bankers” such as his father were more furious than anyone else about what has gone on.

He also laid into Goldman Sachs, target of a probe by the US Securities and Exchange Commission and also by Britain’s City watchdog, the Financial Services Authority, which yesterday launched its own formal enforcement investigation.

The beleaguered Wall Street investment bank should be suspended as an advisor to the British government until the outcome of the investigation is known, he said.

Splitting the British banks into low-risk deposit-takers and higher-risk investment banks would, Clegg acknowledged, take time, but it would forever change the “ecology of banking.” There would be a 10 per cent levy on bank profits and new “non-negotiable” lending targets for the state-owned banks.

Small businesses would be supported through the creation of local enterprise funds and regional stock exchanges.

As he detailed his plans, support for a break-up of the super-banks came from no less an organisation than the International Monetary Fund, which warned in its twice-yearly Financial Stability Review that time for the reform of the global banking system is running out, particularly as many of the institutions are bigger and more dominant now than they were before the crisis.

Fiona Walsh writes for the Guardiannewspaper in London