A change of fortune for the City superheroes?

When the credit crunch passes its nadir, the words of Warren Buffett, the Sage of Omaha and legendary investor, may come back to haunt a few of this country's most high-profile multimillionaires. "You only find out who's been swimming naked when the tide goes out," he said.

Over the past few years, some of the UK's best-known entrepreneurs have made their fortunes on the back of the boom in credit that drove the global economy to the top of the hill and back down again.

The likes of Robert Tchenguiz, the Reuben Brothers, Sir Philip Green, the Candy Brothers, Nick Leslau, Mike Ashley and Sir Tom Hunter have all made their loot from banks providing them with access to huge debt capital in order to conduct highly leveraged deals.

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These dealmaking kingpins have far more in common than their bulging bank balances. They have often invested in, or played key roles in putting together, the same blockbuster deals in property and retail. Often the chief financier who helped provide the lending power to stitch deals together was Peter Cummings, the head of the ailing HBOS's corporate banking business.

The quietly spoken Scotsman has long boasted that he sticks by his clients through the tough times. But HBOS's £40bn of loans to construction and real estate companies was part of the reason for investor fears that nearly caused the bank to implode last month before a rescue deal with Lloyds TSB.

Mr Cummings' profile rose after he backed Sir Philip's lucrative acquisitions of Bhs and Arcadia early this decade. But later deals have not gone so well. Mr Cummings was the linchpin in the £1.1bn takeover of the retirement home builder McCarthy & Stone in 2006, assembling Sir Tom, Mr Leslau and the Reuben Brothers as investors and buying a 20 per cent stake for HBOS.

This is just one of a plethora of deals over the past decade where the entrepreneurs put their hands in their pockets, with the help of plenty of debt, and made mega-deals a reality. Until a year ago, many of the deals looked to be sound business. For instance, Mr Tchenguiz had built a 10 per cent stake in Sainsbury's ahead of what was expected to be a £10.6bn bid for the grocer by the Qatar Investment Authority (QIA). However, the deal spectacularly collapsed last November and on Wednesday Mr Tchenguiz was forced to sell his stake as a result of the financial difficulties of the Icelandic bank Kaupthing, which left him nursing losses of £600m in a single day.

In fact, the credit crunch, which influenced the QIA's decision to walk away, has hit some of the billionaire's deals like a juggernaut, although most of them still have hundreds of millions in the bank – for now.

But as the credit crunch enters its most volatile and precarious period, what is the current state of these multimillionaires' bulging coffers and how far will their swimming costumes have slipped once the tide goes out?