At midday tomorrow, the international Olympic Committee will decide which city will host the 2012 Olympic Games. As London lines up its big hitters ahead of the vote, Chief Sports Writer Scott Wilson explains how our chances are too close to call.

BARON Pierre de Coubertin, the founder of the modern-day Olympics, once famously observed that "it is not the winning but the taking part that counts". He had clearly never been involved in a bidding process to host the Games.

Tomorrow lunchtime, in the glistening tower block of the Raffles City Convention Centre in Singapore, delegates from five cities will learn who has won one of the most lucrative races of all time. For four of the hopefuls, having taken part in the contest will count for nothing if all they are left with is a collection of shattered dreams and a bill of some £30m.

The cost of the bidding process has been substantial but, for the five cities in the running - London, Paris, Madrid, New York and Moscow - the potential rewards are even more astronomical.

The British Government believes the Games would promote urban regeneration, employment, health and tourism, and totally transform the run-down Lower Lea Valley in the east of the capital.

That is why, with the 116 IOC members preparing themselves for tomorrow's secret ballot, the heavy hitters are in town.

Tony Blair jetted into Singapore on Sunday evening, with David Beckham, Sir Steve Redgrave and Dame Kelly Holmes in tow. French president Jacques Chirac will delay his arrival at the G8 summit to push the case for Paris, while Muhammad Ali has been pressing the flesh in New York's cause.

But while the IOC members have been known to be easily influenced in the past - ten were expelled for selling their votes for favours in the aftermath of the decision to award Salt Lake City the 2002 Winter Games - current president Jacques Rogge is confident this week's vote will reflect the multiple ebbs and flows since the first formal bids were published in July 2003.

Rogge is also expecting the final outcome to come down to "no more than half a dozen votes", with leading Olympic analysts predicting a two-way tussle between London and Paris once the early rounds are out of the way.

"It's hard to point to a glaring weakness in either bid," explains Ed Hula, an Olympic movement commentator who runs the Around The Rings Website. "It's tough to tell them apart. It's evens."

Yet, while Paris remains the favourite in the eyes of the bookmakers, it is London that is finishing with a potentially decisive surge.

A little over a year ago, the British bid was in disarray. American businesswoman Barbara Cassani had just stood down from her role as leader of the bid committee and the IOC had produced an initial evaluation report that raised serious concerns about London's "obsolete" transport system and criticised some of its venues.

The subsequent 12 months have seen a radical turnaround, with much of the credit having to go to Cassani's replacement, Sebastian Coe.

As a middle-distance runner, the two-time Olympic champion was famous for tracking the leaders at the back of the pack before swallowing them up with a mighty sprint finish. If London is successful tomorrow, he will have timed his last-minute surge to perfection yet again.

Coe's first move when he was appointed was to tackle the bid's perceived weaknesses head on and that, more than anything, ensured last month's all-important report from the IOC's evaluation committee placed London only marginally behind its French rival.

The Prime Minister was enlisted to provide promises about the funding needed to improve the capital's dated transport infrastructure, while London mayor Ken Livingstone was brought on board to extol the city's multi-culturalism and ethnic diversity, something that sits well with the Olympic movement's ideals.

Just as significantly, though, Coe's status as a former gold medallist has enabled him to excel at the schmoozing and politicking that inevitably accompanies any Olympic vote.

The IOC members recognise him and like him. When he talks of the immense impact of an Olympic Games, no-one can doubt the sincerity of his words. In an environment riddled with empty platitudes and vacuous promises, Coe is one of the few people who walks the walk as well as he talks the talk.

"London has done very well, especially since Seb Coe came in," said an unnamed IOC member last weekend. "He's so impressive and very respected as a sportsman among IOC members. It's impossible to say that London will win, but what's for sure is that he's turned the bid around."

He has seduced not only the IOC's members. When Coe was appointed, London trailed all four of the other cities in terms of public support. Today, only Madrid can better the 81 per cent of people who backed the bid in a recent Government survey.

Ultimately, though, that support is not enough to win the Games. Everything will come down to the votes of the IOC's 116 members.

Tomorrow, each bidding city will make a 45-minute presentation before fielding 15 minutes of questions. The members will then receive a copy of the evaluation committee report before casting their first secret ballot. And it is here that the real lottery will begin.

Even if London receives more votes than any other city, it will not be awarded the Games unless it polls more than 50 per cent of the votes cast.

Given the regional alliances that tend to dominate the opening round of voting, this is all but impossible and, instead, the city polling fewest votes will drop out of the contest ahead of the second round.

This will continue until there are only two cities remaining, meaning the contest will almost certainly be settled by the second or third-preference votes of those members who backed a loser in earlier rounds.

If the latest predictions are anything to go by Moscow and New York are expected to be the early victims tomorrow.

That will leave London, Paris and Madrid, with Coe's team anticipating the latter falling at the penultimate hurdle.

This will make kingmakers of the 25 members who have supported the Spanish capital to that point, and the London team has spent the last month courting the IOC delegates from South and Latin America who are expected to vote for Madrid in the early rounds.

They have been privately pleased with their response but, once the door closes on the voting chamber tomorrow, the outcome will be out of their hands.

"Winning this race would top everything else I have achieved in my career," said Coe last weekend. It would also change the face of British sport in an instant.