Sebastian Vettel kept his slim World Championship hopes alive this weekend with a stunning victory in the Japanese Grand Prix. The 22 year old had to win the race to stay in contention for the title, and if the result at Suzuka is inexplicably repeated in the final two rounds he will finish the year as World Champion.

2009 has very much been a season of two halves. Jenson Button dominated the start of the year and claimed six wins from the first seven races, an achievement equalled only by Jim Clark and Michael Schumacher. At that rate Jenson could have wrapped up the championship at Spa Francorchamps.

However, Red Bull introduced an exceptional technical update to their car at the British Grand Prix and made themselves the new benchmark team. At the same time, Rubens Barrichello grew more comfortable with the Brawn chassis and started outperforming his teammate. Jenson’s run of success came to an end and in the last eight races he has averaged just sixth place.

The result is that three drivers now have a shot at the title with two races left on the calendar. Jenson Button is on 85 points, 14 ahead of Barrichello and 16 ahead of Vettel.

Championship victory for Vettel is not very likely but is still an outside possibility. Kimi Raikkonen overcame a larger gap to beat Lewis Hamilton in 2007, and McLaren was a lot stronger two years ago than Brawn is now. Red Bull brought updates to the RB5 at Singapore and comfortably had the fastest car on the grid in Japan, so with further updates arriving in both Brazil and Abu Dhabi they should be very hard to beat.

Sebastian Vettel will now be ruing the mistakes he made earlier in the year that cost him valuable points. His crash with Robert Kubica at Melbourne, his crash with the wall at Monaco, and his crash with Kimi Raikkonen at Budapest all cost him points. If you also consider his speeding penalty at Singapore, and the overtaking manoeuvres that Button placed on him in Bahrain and Turkey, Vettel could actually be leading the championship right now.

Instead, Sebastian is in third place and requires two victories to stay in the title hunt.

If Vettel does overcome the odds he will become youngest ever World Champion, adding to his record as the youngest ever points scorer, pole sitter, and race winner.

Crucially, Vettel can rely on the help of his teammate, something which Button cannot. Mark Webber will be fast in the final rounds and will be in a position to interfere with the Brawn cars, or at least steal points off them. Webber isn’t going to ram anyone off the road, and he isn’t going to bend over backwards to see his teammate steal the glory, but he will still be an effective tool for Red Bull in the last two races.

Meanwhile, Jenson has to keep a close eye on the other side of his garage.

Rubens Barrichello remains Button’s biggest threat to the world title. Since the Turkish Grand Prix Barrichello has been the strongest Brawn driver and has taken a pair of victories along with a third place, whilst Button has managed just one second (behind Rubens) and a string of minor points finishes.

If the Brazilian is going to upset Button for the title, he will do so with a big result at Interlagos where he is always quick. The circuit passes his grandmother’s old house and it will be the first time in his long career that he has raced at home in the heat of a championship battle. With nothing to lose he will be highly motivated.

Rubens can take the drivers crown with two second places in Brazil and Abu Dhabi, but only if Vettel doesn’t win both and Button fails to score. That scenario is highly unlikely so Rubens is simply aiming to stay in the hunt for as long as he can.

Although Button is clear favourite to win the World Championship, and even seal it with a race remaining, he is under a huge amount of pressure. The Brit has everything to lose and the strain of being hunted – as opposed to being the hunter – has already started showing.

Jenson lost his cool during a press conference at Spa when a journalist questioned his motivation. Button was very defensive about the line of questioning, and although it’s very easy to read too much into that, it was clear that the happy and chirpy Jenson from Melbourne was gone. He has admitted that racing is a much bigger part of his life now that he is winning, so will be feeling the sort of pressure that he hasn’t let himself feel before.

Button has lost positions during the first lap in six of the last eight races so is driving more cautiously than he was at the start of this year in Bahrain where he barged past Vettel and Hamilton shortly after the start.

Interestingly, Button is yet to sign a deal with Brawn for 2010 as he is disputing the money being offered to him. Jenson took a pay cut at the start of this year to help ensure the team survived, but now that Brawn has well and truly found its feet, Button is expecting to be duly rewarded. Brawn seems less keen on the idea and is only offering the champion elect a modest increase.

Button’s manager said “We aren’t being greedy. When we signed the deal last year we did so in the knowledge that if all went well for the team, things would also go well for Jenson.”

Whilst the contract negotiations shouldn’t effect Button’s on track performance, it can’t be good for Jenson to have a thought deep in his mind somewhere that he end up losing the title as well as his seat, which would be an absolute disaster given how close he is to conquering the world.

Barrichello and Vettel need every slight advantage they can get, and the fact that Button is in a disagreement with his team (even though it’s via his management and will surely be resolved) will be something that will give them a mental boost.

At least Button still has mathematics on his side.

Jenson needs just six points in two races (two sixths, or one third) to become World Champion regardless of where Rubens and Sebastian finish. If his rivals fail to win, the equation gets even better. Button is looking pretty good and could easily seal the title in Brazil.

Reliability is also in his favour.

Sebastian Vettel is now on the final engine from his allocation of eight after two failures in Valencia. The unit he used at Monza, Singapore, and Suzuka must also last him in the final two races as well or he will receive a penalty. The engine will be under a massive strain already from the three races it has contested because Monza is extra fast, Singapore is extra long and hot, and it was pushed hard in Japan where Sebastian went for the win. A ten place grid penalty will surely take him out of title contention, as will another engine failure, and Vettel is unlikely to finish the year without either occurring.

Meanwhile, Button can use a fresh engine for the final two races. None of his other seven Mercedes units have had a failure so only monumental bad luck would bring him to a halt now.

McLaren’s resurgence will also work to Jenson’s benefit. Lewis Hamilton will be a contender for victory in the final two races and that will mean he could steal big points off Vettel and Barrichello. Toyota’s drivers have also rediscovered their early season form so could have a good enough run to spoil the party as well.

Jenson has a decent points margin so whatever happens at Interlagos he will go into the final race at Abu Dhabi with at least four of them up his sleeve. If he finishes ahead of both Barrichello and Vettel in either of the final two races, the championship is his, and if he can’t manage that he just has to shadow them.

It would be an amazing success for Jenson Button and although his late season form has taken the shine off his success it is still a great Formula One story. The highly talented driver who got stuck in dismal machinery but stayed loyal to his team through its darkest hour is about to claim the sport’s biggest prize.

Like most fairytales, this one could still have a twist in the tail.