© Will WilntercrossThe swimming pool stretches 215ft into the distance under a cloudless Montenegrin sky.
Superyachts, models and the infinity pool - welcome to Nat Rothschild's £1m birthday party.

Giant silver glitter balls float serenely on its surface while all around workmen saw, hammer and polish in last-minute preparations for what promises to be the party of the century for this tiny, newly-independent nation.

While the rest of the world struggles to come to terms with an era of austerity, there will be no such concerns tonight for Nat Rothschild, the billionaire British investment banker, as he celebrates his 40th birthday with an elite band of 400 fabulously wealthy friends.

The Oxford-educated entrepreneur, the scion of the Rothschild banking dynasty and one of the world's most eligible bachelors, is spending an estimated £1 million on three days of lavish celebrations in Porto Montenegro, a £518 million new marina resort on the Adriatic Coast.

He is one of the main investors in the exclusive development of boutiques, apartments and restaurants which, when finished in a few years' time, will provide berths for 630 yachts and aim to out-bling the likes of St Tropez and Monte Carlo.

The guest list for the event is "very, very secret", according to one of the Montenegrin organisers, but is thought to include Lord Mandelson, Oleg Deripaska, the billionaire Russian aluminium oligarch, Mr Rothschild's parents, Jacob, the fourth Baron Rothschild and Serena, and Tony Hayward, the former head of BP.

George Osborne, the Chancellor of the Exchequer and a contemporary of Mr Rothschild at Oxford, is unlikely to risk incurring the wrath of financially-squeezed middle England by attending the glitzy event.

It is a big deal for Montenegro, which since gaining independence from Serbia five years ago has pinned its hopes of economic revival on tourism.

"We've never seen anything like it," said Marko Cirkovic, a waiter in the unremarkable town of Tivat, which surrounds the marina complex. "In fact Montenegro has never seen anything like it. This is a huge thing for our country."

The select band of billionaires, bankers and models who do come will sip champagne cocktails around the newly-built "Lido Mar" pool when the birthday celebrations begin in earnest, bringing a touch of French Riviera-style glamour to an all but forgotten part of the Adriatic in one of Europe's smallest and poorest countries.

The pool, which is lined with black and white mosaic tiles and overlooked by shaded seating areas, provides stunning views of the World Heritage-listed Gulf of Kotor, Europe's southernmost fjord.

DJs will play music while Mr Rothschild's guests lounge on the teak deck and in pavilion-style cabanas, their view of the water framed by palm trees imported from Uruguay. The pool is built over what was once a submarine dry dock, when Tivat was a Cold War-era naval base.

The three-day birthday party has been organised by Fiona Leahy Design, a London-based event company that counts among its clients Dita Von Teese, the American burlesque artist, Jade Jagger and Louis Vuitton. The party is also cloaked in secrecy. "I can't give you any information at all, we've all had to sign confidentiality agreements," a spokeswoman for Fiona Leahy Design said.

Colin Kingsmill, Porto Montenegro's marketing manager, who previously told a magazine that the guest list would include some of the wealthiest and most photogenic people in the world, was similarly tight-lipped. "It's a completely private event," he said.

Many locals have welcomed the building of the marina - the pet project of Peter Munk, an 83-year-old Canadian gold magnate - but others say it has divided Tivat into a gilded ghetto for the uber-rich and a drab Communist-era town where buskers play barefoot.

But that will be of little concern to the beautiful people when they gather for what is being dubbed the biggest social event in the short history of one of Europe's youngest countries.