'We want 2009 to be our year, so we're going to start making an impression very early on," declared Bono, in his usual understated way, as the band put the final touches in London to its latest album No Line On The Horizon late last year.

So far, the U2 frontman has made good on his promise. It's been hard to escape the band's marketing juggernaut of late.

There was the week-long tie-in with the BBC, under the slogan BBC=U2, which included trailers and a series of live events, including a rooftop concert in central London, and a section on the BBC website offering tickets and links to the band's official site. The promotion is worth about stg£1m (€1.1m), according to industry experts, but on a public network that doesn't accept advertising, it's actually priceless.

As No Line On The Horizon rocketed up the UK charts, with first-day sales of 65,000, the band jetted to New York for a week-long stint on the iconic US chat show, David Letterman.

On Tuesday, New York Mayor Michael Bloomberg turned out for the temporary re-branding of part of Manhattan's West 53rd Street to 'U2 Way'. It's difficult to estimate quite how much that is worth publicity-wise, but experts place it safely within the range of several million dollars.

If U2 don't score a few Grammys for the album, the band's marketing team certainly deserves to sweep the board at the next global marketing love-in. As campaigns go, the launch of No Line On The Horizon has been pitch-perfect.

It also underlines the paradox at the heart of U2's success. The self-styled 'Four boys from the northside of Dublin', with their impromptu rooftop concerts, are actually a carefully manicured brand around which throbs a global corporation to rival any multinational giant.

The late Jim Aiken probably put it best. "U2 are arch capitalists but it looks as if they're not," said the concert promoter.

At last count, the U2 empire spanned 19 different corporate entities, not including band members' other business interests in venture capital, commercial property, clothing and internet companies. Some of the companies, such as a defined benefit pension vehicle, are unlimited and don't have to file accounts. Others, such as U2 Limited, which licenses the band's music copyright, publish limited accounts that show relatively small profits, if any at all.

For example, in 2006 -- the year after the band's top grossing tour Vertigo -- one of the companies, U2 Limited, posted a small profit of €3.84m after paying corporation tax of €765,578.

Meanwhile, Not Us, considered to be the main holding company behind U2's business interests, reported a net loss of €2.91m in 2005, having given..... unsecured, interest-free loans to subsidiaries. Two years previously, Not Us reported debts of €18.8m, most of which were owed to U2-controlled subsidiaries, including U2 Limited which was owed €4.7m.

Get the picture?

The profits, indebtedness or financial health of any one of U2's business entities at any one time offers little real information about the band's fortunes. Money-flows between the companies are mostly unseen. According to industry experts, the whole point of having such a complex corporate structure is to minimise tax.

In mid-2006, the band's management shifted several key entities to the Netherlands to avail of a more lenient tax regime and avoid the scrapping of Ireland's artists exemption on earnings over €250,000. The shift is believed to have saved the band €15m a year.

Dick Molenaar of Dutch-based All Arts Tax Advisers described it as a smart move by U2's advisers, even aside from the Irish tax implications. "Since Ireland has a zero tariff on outward royalties, many countries try to tax royalties from Irish groups within their own borders. By introducing a Dutch daughter company, U2 can avoid this by first booking their royalty income to the Netherlands, and then on to Ireland," he said.

But it is possible to glean some information from U2 Limited's accounts. It's a fairly safe guess that the five employees of that company are the four members of the band and manager Paul McGuinness, although this is not stated in the accounts. Wages for the five employees of U2 Limited in the latest accounts for 2007 were €21m, which breaks down as €4.2m each. The previous year, 2006, the five employees took home €17.96m or €3.6m each.

But music, while central to the U2 brand, is only one part of the U2 business empire. To understand the broad range of current business interests, it's necessary to go back to the band's humble origins.

Much of U2's success has been credited to manager Paul McGuinness. He set up his company Principle Management in 1984. Legend has it that U2 started out on IR£25 pounds (€32) a week, plus expenses. Their bus fares supposedly came from a jar of coins sitting on McGuinness's desk. Then came the huge success of their 1980 debut album, Boy.

By the mid-90s the band was selling about eight million records a year and generating $120m (€95m) in earnings.

Unlike many other rock and pop bands, U2 own copyright to their songs, all of which were written by the band. It means that U2 receives all of the royalty income whenever one of its songs is played. The Beatles' sound recordings, for example, are owned by EMI Group.

In 1985, when the record company Island Records was in financial trouble and was unable to pay royalties, U2 took a 10pc stake in the company in exchange for waiving royalties. Four years later, Island Records was acquired by Royal Philips Electronics and the band received about $30m (€24m) for its stake.

But, according to Bono, much of the profit from the Island deal was lost on poor investments. "We put it in the hands of some people whom we liked personally, but weren't as expert as they thought in the areas that they were investing in. On the positive side, it made us take more charge and interest in our business."

During a very high-profile fall-out between McGuinness and U2's accountant and adviser at the time Ossie Kilkenny, the band members remained loyal to their manager.

Insiders say McGuinness hung on to his 20pc share of the U2 pot by promising to make the pot bigger and the business more efficient. He recruited Trevor Bowen, a former senior partner in the KPMG accountancy practice, as financial director and replaced Kilkenny with KPMG as the band's auditors.

Dublin's Clarence Hotel was the first foray into commercial property by band members Bono and The Edge. They teamed up with Dublin businessman Harry Crosbie to acquire the Liffey-front property.

The hotel struggled initially. Its holding company, Brushfield, had accumulated losses of €11.2m at the end of 2003 and Bono was forced to give a loan of €4m to keep it up and running.

Despite this, Bono has remained the band's lead investor outside of music. He launched a clothing range with his wife Ali Hewson, called Edun (nude spelt backwards). He is also involved with the venture capital firm Elevation Partners, which claims to have $1.9bn (€1.5bn) in committed capital to be invested over the next six years. It is a minority shareholder in the publishing giant Forbes, the technology company Palm (of Palm Pilot fame) and marketing company MarketShare Partners, among others.

All the band members, along with manager Paul McGuinness, are avid art collectors. McGuinness has one of the largest and most valuable private art collections in the country, according to a recently published book on the Irish art world, Sold!

Adam Clayton is said to have a good eye for painters on the rise. For example, last year a band-owned painting by Jean-Michel Basquiat, which Clayton picked up for a few hundred thousand dollars, sold at Sothebys for a whopping €6m.

Other band investments include the Californian internet company Burst.com.

But the real change in U2's fortunes has come about because of a far more professional and shrewd approach to managing its music interests, particularly tours.

The Elevation Tour in 2001 made €118m, topping the tour charts that year, despite competing with boyband favourites N-sync and the Backstreet Boys. The U2 lads, well into their 40s at that stage, played 113 concerts in just 12 months.

The Vertigo tour in 2005 was the second most lucrative tour of all time, according to Billboard magazine, netting an estimated $389m (€307m).

According to McGuinness, the concert was seen by 3.3 million worldwide.

Merchandising provided an additional $10-$12 (€8-€9.50) per head in the US and $8-$9 (€6-€7) per head in Europe. "Merchandising is very important, and it tends to be an integer of how hot the band are," he said.

In 2004, the band signed a deal to put its entire back catalogue and its new album, How To Dismantle An Atomic Bomb, on Apple's iPod. The following day shares in Apple rose close to an all-time high, adding about $2bn (€1.6bn) to the value of the company. It was the most lucrative online music deal of any rock band in history.

Last year, U2 signed a 12-year deal, believed to be worth €154m, with concert promoter Live Nation for the rights to the band's tours, merchandising and website for the next 12 years.

But the deal appears to have gone sour already. In December, it was announced that U2 is selling shares it received as part of the deal for $25m (€20m). According to The Wall Street Journal, Live Nation stands to lose $19m (€15m) from the U2 share sale.

There's been a setback too for the much-publicised U2 Tower in the Dublin Docklands. The Development Authority put the Tower on hold for 12 mon-ths late last year to allow property and financial markets to improve.

Despite the phenomenal value of the U2 brand and the undoubted success of the initial marketing campaign for this latest album, U2's finances are not so high that they can't be dragged down by the current economic slump. The band has promised cheap tickets for concerts in its forthcoming tour, but there is little by way of detail on this. Cash-strapped fans are certainly less likely to fork out for merchandising in the way they did four years ago.

U2's fans are also getting older. The band's latest single Get On Your Boots hasn't rocketed up the charts in the same way as their album. Older fans buy albums; younger fans buy singles.

It's not surprising that Bono says he is stung by accusations of hypocrisy over the band's tax affairs. U2's right-on, save-the-world credentials are a key part of the brand. The last thing U2 needs right now is to be seen as the arch capitalists Jim Aiken once claimed they were, especially when workers throughout the world are losing jobs and homes, and even economists are talking about the demise of the old capitalist order.