Sir Richard Branson is knackered. So far this week he has displayed his trademark, toothy grin at the launch of the latest addition to the Virgin Atlantic fleet - the world's longest aircraft - at the Farnborough air show; chatted to bemused trainspotters during the inaugural journey of one of his fleet of Virgin Rail tilting trains; and he has just stripped with the cast of the Broadway version of The Full Monty 100 ft above New York's Times Square on a giant mobile phone to mark the launch of Virgin Mobile in the US.

Frankly, he could do with a drink and is seriously considering falling off the wagon at his launch party later.

"99.9% of the time I still love this, but it is getting to be hard work. It is rare for me to stay out of the bar like I did last night but knowing that I had to get up at five in the morning, I decided for once to be sensible," he says as he sits in the basement of his Times Square Virgin Megastore waiting for yet another well-manicured American news anchor to show up and interview him.

"Ten years ago I would have had no problem being up all night partying and then doing CBS and CNN in the morning, but now I am just beginning to realise that there are some limitations."

It's also a feeling that some in the business community are having about the empire which he has ruled since he set up Virgin over 30 years ago.

Since the September 11 attacks, which sent Virgin's chief money spinner, Virgin Atlantic Airways, into the red, it has become increasingly apparent that cash is king in the Virgin empire.

Branson has raised an estimated £1.3bn from the sale of parts of his empire in the past three years. Almost half that amount came from the sale of a 49% stake in Virgin Atlantic to Singapore Airlines in 1999. But getting such large deals awayin the current market turmoil is tough, which is why some commentators have suggested that a recent spate of small-scale deals - selling a 55% stake in Virgin Active health clubs and dumping a Majorcan hotel complex - point to a growing cash squeeze.

Virgin's financial engineers deny that the empire is running out of loot, saying that, while it is about $300m to $400m in hock to its banks, the group has a cash pile of several hundred million dollars.

But talk of a funding crisis gained momentum recently as Branson's advisers, led by his version of Alistair Campbell, former helicopter pilot Will Whitehorn, suggested that some of the Virgin businesses could be headed for the stock market.

Branson's last experience of the public markets - excepting budget airline Virgin Express which has a partial listing in Brussels - was anything but glorious. He floated the Virgin Group in December 1986 but bought it back into private hands after just two years, complaining that the City suits did not understand his business and were too short-termist.

So why is he coming back to the market then? The problem is that for the last few years Branson has been tapping other businessmen, selling them stakes in Virgin companies. Initially he brought in partners after his ventures had proved themselves, as he did with Virgin Atlantic, but lately he has been bringing partners in before launch. And frankly, some of them want a return.

"The only reason for us to consider floating any of our companies - and it is not something... I am keen on - is if our partners want to realise their investment."

There are obstacles, chief among them the labyrinthine finances of Virgin. Money moves in and out of the 275 Virgin-branded business through an assortment of off-shore companies and trusts. While these complex financial arrangements are all perfectly legal, in an era where investors are increasingly concerned about financial transparency following the scandals at Enron and WorldCom, it is debatable how appetising the markets will find Branson's empire in its present shape.

Branson, however, is adamant that - using the slogan of Virgin Mobile USA - he has nothing to hide. He points to the long list of partners, from financial giant AMP to Deutsche Telekom, that he has attracted as proof that he is kosher.

"We actually genuinely do not have anything to hide and it does not matter to us what is written about our finances as long as we pay our bills and all our staff get paid," he says.

"What people should be asking themselves is: 'What is Richard Branson's track record? Has he ever let a company go bankrupt?' The answer is no. 'Has he ever had any spectacular failures?' The answer is no, and 'Will the reputation of this company be damaged by some other Virgin company going horribly wrong?' And all I can say is that our track record is no, there have been plenty of sceptics out there who have waited for us to stumble and either they have not understood or they have not wanted to understand how our companies work."

Virgin's offshore status has been crucial to its development: it allowed money to move from business to business without massive tax liabilities. "If we had not done it the way that we did, Virgin would be half the size that it is today," argues Branson.

There is no escaping the fact that offshore vehicles worry the market. In fact the Treasury looks set to change the rules, raising the prospect of Branson coming back to the UK. He adds that he believes it possible to bring most of the companies back onshore, if the government's proposals are made law.

Returning to the stock market would raise another issue - that of Branson's own role. He knows full well that he is not in the same mould as your typical City chairman. "If we floated any of our companies I would most likely become titular president, somebody else would be chairman and somebody else would be chief executive. I would let other people have all the dealings with the public market. That is not where my skills are. What I love doing is starting new companies."

Of all the Virgin businesses Virgin Mobile in the UK is the most obvious candidate for flotation. After three years it is cash positive, having grown from being something of a late entrant to the market into a serious niche player. It cost about £200m to get to this point, but Branson only had to stump up £50m. The bulk of the cash, £100m, came from a bank loan arranged by a small syndicate lead by Virgin stalwarts Royal Bank of Scotland and JP Morgan. T-Mobile put in the rest.

Virgin does not expect to take any cash out of the business for two more years, but all the signs on an operational level are pointing in the right direction for an IPO.

Which takes us to why Branson has just been dangling naked over downtown New York (in fact he wore an anatomically "corrective" body suit - he is 52 years old, after all). Virgin Mobile's no-nonsense pre-paid business model, sculpted by UK head Tom Alexander, is now being drop-kicked into the North American market.

The $160m that Branson is spending over the next two years - cash left over from the Singapore Airlines deal - is the most he has ever spent on a start-up business. The stakes are high, but so are the potential rewards. Branson believes that revenues at Virgin Mobile USA could outpace Virgin Atlantic's $2.1bn a year.

Virgin's advisers are already working on more funding. They have held talks with a number of American private equity groups and a deal, which would see Virgin and US wireless partner Sprint reduce their stakes, is planned for 2003.

Talk that up to eight businesses could be detached from the Virgin mothership over the coming eight years may well turn out to be as full of hot air as one of Branson's balloons. He thinks he may have enough cash to avoid having to deal with the City again.

"The alternative is that if we are cash rich at the time and if one of our partners wants to float we could work out the float price and buy them out and remain private," Branson says.

Certainly he does not see any more big cash-devouring start-ups so soon after the investment in Virgin Mobile USA. But then again, he never says never. "Quite often when we have just launched a new business, people ask whether that's it for the moment, and then five months later we are back again. I am not good at saying no," Branson admits.

"I had the wife of [CNN broadcaster] Larry King fly down to see me last week with a new invention that would help people learn the guitar in a day - it was a really exciting idea and I thought "I have got to say no, I have got to say no". But I haven't, yet."

And will he be able to say no to the demon drink at this evening's swanky bash? "I think I am just sort of coming out of a dry period now," he remarks slyly. "Rules are made to be broken."

The CV

Born: July 18 1950

Education: Stowe School (left at 15)

Career:

1969: Virgin brand launched as mail order record business and became music publishing operation in 1972. Shortly afterwards Branson makes first million with release of Mike Oldfield's Tubular Bells (At the time, Branson thought perhaps it needed lyrics). 1984: Virgin Atlantic Airways formed;

1986: Virgin Group floats on stock market (bought back two years later);

1987: Branson crosses Atlantic in balloon;

1998: Branson invests in railways; 1999 he launches Virgin Mobile and is knighted;

2000: he fails to win National Lottery bid

Family: Wife Joan, children Holly, 21, and Sam, 16

Hobbies: Ballooning, sailing and the occasional publicity stunt.