Afternoon folks. So we've arrived at the 20th Grand Prix of the season. In a little over two hours we'll know the F1 world champion.
Let's have a look at this afternoon's permutations for the championship...
Vettel will win a third straight title if he finishes anywhere inside the top four.
If he fails to do so, Alonso can snatch the crown if he wins and Vettel is lower than fourth, is second and Vettel is lower than seventh or is third and Vettel is lower than ninth. Make sense? I hope so.
At the front of the grid it's a McLaren
lockout while Red Bull
dominate the second row, with Mark Webber
ahead of teammate Vettel.
Expect Webber to let Vettel through if he remains ahead of the German.
is racing for the last time for McLaren
and he has just sent his well wishes to all the team.
It is spitting with rain on the grid! Whether that will affect the start is not yet known.
Button tells Sky Sports F1 that he can win the race and doesn't care about the championship battle around him.
BBC Sport's David Coulthard tries to walk alongside and interview Vettel but the German is fully in the zone.
There's so many stories surrounding today's race with the championship battle, Hamilton's last race for McLaren and also legend Michael Schumacher's final race in the sport.
15 minutes until lights out.
Time for the Brazilian national anthem. It's always a fantastic place to end the F1 calendar in Sao Paulo.
McLaren team principal Martin Whitmarsh tells BBC Sport that "anything can happen" as Alonso has nothing to lose.
The Spaniard does need to be wary not to crash out, however, as if he was to do so then Vettel would automatically be awarded the title.
An emotional Schumacher did a lap of the circuit flying a flag out of his car. Today sees the end of a quite marvellous motor-racing career.
The veteran tells reporters that he expects a "beautiful" end to the season. The rain continues to spit.
It's a short rundown to the first corner at Interlagos. Can Alonso move up and get in amongst the Red Bulls? Will the McLarens blitz away from the field at the front? I can't wait!
There's a slight mist on the grid but it's believed that there's not enough moisture to seriously affect proceedings. However, a slightly wet visor could mean impaired vision.
A quick reminder of the top 10: 1 Hamilton 2 Button 3 Webber 4 Vettel 5 Massa 6 Hulkenburg 7 Alonso 8 Raikkonen 9 Rosberg 10 Di Resta
It is expected to dry up and the wet tyres are being taken back to the garage.
Hamilton sets off on a single circuit of the track before we get underway.
This is a crucial period when the drivers warm up the tyres and get in the zone for the decisive start. Not long now.
The track does look quite slick but as mentioned there's not expected to be enough to trouble these seasoned pros.
Hamilton is ready and waiting for the rest, we're ready. Here we go.
We're underway in Brazil!
Great start for Alonso, Hamilton's away!
Vettel's down in seventh! He's crashed!
I REPEAT! SEBASTIAN VETTEL HAS CRASHED!
At the start of the second lap Alonso passes Webber and Massa to move up to third.
Home favourite Bruno Senna is also out.
Vettel is told over the radio that if it is physical damage aside from the front wing then he'll have to retire.
However, he seems to not have picked up damage and sets the fastest lap of the race. He's way down in 20th place though.
Replays show that Vettel took two hits on the opening lap and seemingly has no damage. The boy is lucky.
TOP 10 UPDATE: 1 Hamilton 2 Button 3 Hulkenburg 4 Alonso 5 Webber 6 Massa 7 Di Resta 8 Raikkonen 9 Kobayashi 10 Rosberg
Alonso has gone wide and that allows Hulkenburg to take the third place Alonso so badly needs.
I still find it amazing that Vettel has not sustained damage after those hits on the opening lap. He's continuing to move up places at the back.
Grosjean crashes out as Button challenges Hamilton for the lead and Webber spins out to move to the back of the field. Unbelievable action.
The drives are beginning to struggle to with the wetter conditions and they may need to come in for intermediates soon.
Button passes Hamilton for the lead.
Unbelievably, Vettel has worked his way up to seventh place.
The German is told on the radio: "It's a long race, just keep the car on the black stuff."
The rain is falling heavier now than it was at the start. Surely there'll be some tyre changes soon?
Button is now pulling away from Hamilton at the front as Webber comes in to the pit. He's now down in 19th.
Hamilton comes into the pits for a set of intermediates.
Championship rivals Alonso and Vettel also enter for a set of intermediates.
Button was due to come in as well but he tells his team "It's stopped raining". He stays out on his slick tyres.
Vettel and Alonso have dropped down the field because of their stops. Vettel is 17th, Alonso 12th.
TOP 10 UPDATE: 1 Button 2 Hulkenburg 3 Hamilton 4 Massa 5 Vergne 6 Alonso 7 Kovalainen 8 Glock 9 Petrov 10 Pic
Hamilton goes much quicker than Button and that means that the track is coming to the intermediate tyres.
That top 10 is very jumbled because of the difference in tyres between all the drivers.
Hamilton reports back that the intermediates are going off. There's still so much that could happen!
Remember, Alonso and Vettel are both on the intermediate tyres. Will they have to change again soon?
Vettel up to fifth and now just a place behind Alonso.
Massa comes in and on go a pair of intermediates. Maybe they are still required?
Hulkenburg is all over the back of Button at the front of the race.
Both Hulkenburg and Button are the only two frontrunners not to have stopped and they're fighting it out for the lead. Hulkenburg looks far more confident, mind.
Vettel is told that he is the fastest car on intermediate tyres as Button and Hulkenburg go two seconds quicker than the rest. It's so topsy-turvy at Interlagos!
Hamilton in third is a good chunk behind Button and Hulkenburg. The Englishman is told that the rain should stay at this level for 30 minutes but Hamilton says his tyres are nearly out already!
Hulkenburg passes Button for the lead!
Hamilton pits for a set of slicks and so does Alonso. Your move, Seb.
That's a pretty average stop from Alonso. Can Vettel get out ahead of his rival when he pits?
Vettel pits and comes out just behind Alonso!
Rosberg's right rear tyre has suffered a puncture and he'll try to limp back to the pit.
Slow-mo replays show that Vettel's car has suffered a hefty hit but he's able to soldier on. Hamilton sets the fastest lap.
The safety car is out because debris needs to be cleared from the track.
It seems that Button and Hulkenburg will finally pit but they'll surrender a 47-second lead!
TOP 10 UPDATE: 1 Hulkenburg 2 Button 3 Hamilton 4 Alonso 5 Vettel 6 Kobayashi 7 Webber 8 Di Resta 9 Ricciardo 10 Raikkonen
This safety-car intermission gives us a chance to recap what happened on that crazy first lap.
Vettel had a sluggish start and dropped to seventh as Alonso moved up around the outside. The German was then bashed twice but somehow suffered no damage and soldiered on at the back of the field. He has since blitzed his way through the field and now sits just behind Alonso in fifth. In and around all of this there has been tyre changes galore because of the changing conditions. At the front, Hamilton lost his lead to Button in the first few laps but since then, Hulkenburg has surprisingly shot to the front.
The safety car is still out as debris is removed from the tarmac. Rosberg was the man who suffered most with that puncture to his right rear.
The four cars to have been knocked out are Grosjean, Perez, Maldonado and Senna.
Remember, Alonso can snatch the crown from Vettel if he wins and Vettel is lower than fourth, is second and Vettel is lower than seventh or is third and Vettel is lower than ninth.
Hulkenburg is our surprise leader. The German has never had a podium finish in F1.
The top nine cars, apart from Alonso, are on the harder compound of tyre. Fernando is on the mediums.
Surely the safety car will come in soon? Let's get racing again!
Safety car in this lap.
Racing begins again and Hulkenburg blitzes away from the two McLarens.
Kobayashi passes Vettel! Webber was also looking to get past his teammate but went wide and dropped down the field.
Vettel knew that he didn't need to get in a tussle with Alonso but Kobayashi was just far too alert.
Hamilton passes teammate Button for second place. Hulkenburg is doing a fine job at the front.
Kobayashi gets past Alonso! The Spaniard is down to fifth.
Alonso retakes fourth place on the start-finish straight. It's very slippery off the racing line. The drivers have to stick to the drier tarmac.
Massa is applying plenty of Ferrari
pressure to the back of Vettel. He wouldn't take him out would he?!
The answer's no. The Brazilian simply sweeps past the reigning two-time world champion.
At the front, Hulkenburg is loving life as he sets the fastest lap of the race.
As things stand Vettel
will win the world title by seven points. In the constructors' championship McLaren are currently on course to snatch second place from Ferrari
by a single point.
Vettel's damage is supposed to affect his rear grip when turning. He seems to be doing just fine. Rain is reported at turn nine.
Button in third sets the fastest lap.
Just a note that there are 71 laps this afternoon.
The top three of Hulkenburg, Hamilton and Button have pulled away slightly from the next three of Alonso, Kobayashi and Vettel.
Superb wheel-to-wheel stuff from Raikkonen and Schumacher at turn one. They're both fine, no contact. Fabulous control of the car.
TOP 10 UPDATE: 1 Hulkenburg 2 Hamilton 3 Button 4 Alonso 5 Massa 6 Kobayashi 7 Vettel 8 Webber 9 Ricciardo 10 Schumacher
Apologies, that last post may not have been added correctly. Manually refresh the page and all will be well.
The misty rain is back in and around the pit lane. Will there be enough to affect proceedings?
Hulkenburg is now really struggling and Hamilton's closing up with every corner.
Small mistake from Webber and Ricciardo is right on the back of the Red Bull.
Teams are reporting conflicting weather forecasts. Will the rain come into play again?
The lap times are dropping slightly. When will the final stops take place? I'd say in the next ten laps or so.
Hamilton passes Hulkenburg for the lead!
The German got on the white line at the end of turn six and that meant a spin that allowed Hamilton to pass.
The latest forecasts suggest that the rain will stop very soon and that no more precipitation will fall on the track.
This could be disastrous for Vettel's communication with the team, his radio mic is not working.
Interesting move from Rosberg as he puts on a set of intermediate tyres. That's a risky move that could pay off. It's unlikely to work though if there's no more rain.
Vettel's coming in and on go a pair of the medium compound tyres.
The German exits in 10th place. How will Ferrari respond?
Remarkable scenes as Raikkonen drives off the track then attempts to get back on via a side road but it's a dead end! He somehow gets back on track, eventually.
HAMILTON AND HULKENBURG COLLIDE! HAMILTON'S OUT!
Hulkenburg had a good slipstream on the start-finish straight but slid wide as Hamilton gave him plenty of room. Not the way Lewis wanted to finish his time with McLaren.
Vettel has come back into the pit again for intermediates! Alonso is struggling on slicks and is now limping around.
This is so tense.
Amazing replay of Vettel's stop where the team weren't ready for him and had to take the tyre covers off and everything while the German had to sit and wait. Alonso comes into the pit for some intermediates.
Alonso resumes in fourth and as it stands if he goes past Massa ahead of him, he will snatch the title.
Button pits from the lead for some intermediates.
Alonso is up into third and that's effectively second as he has Massa ahead. If he finishes second then Vettel needs to finish outside of the top seven. He's currently ninth.
Vettel now up to seventh and just about safe. This is tough to keep on top of!
TOP 10 UPDATE: 1 Button 2 Massa 3 Alonso 4 Webber 5 Hulkenburg 6 Schumacher 7 Vettel 8 Kobayashi 9 Vergne 10 Di Resta
The rain is getting worse! Full wet tyres may be required!
Hulkenburg was penalised with a drive-through penalty for his involvement in Hamilton's exit.
Alonso will soon pass Massa for second place. He'll need Vettel to finish outside the top seven if he finishes behind Button.
Button's lead to Massa is 19 seconds as the rain continues to fall. What a final 10 laps we have ahead of us.
Alonso passes Massa for second place.
As it stands, Vettel is going to win the world championship by a single point.
Vettel's team reassure him that he's on course to win the championship and tell him to "keep it on the track".
The man in front of Vettel in sixth is fellow German Schumacher and he lets the Red Bull man through! No resistance.
Vettel now needs to lose two places or Alonso needs to take the lead for the Spaniard to win the championship. Both of those are unlikely.
If Button was to make a mistake then Vettel would have to climb two places to fourth to retain his world crown.
Five laps to go.
Vettel is once again told that he's doing enough to win the world title.
Three laps to go. Will we see any late drama?
Kobayashi spins out and that's some places lost for the Japanese driver.
Two laps to go.
CRASH! DI RESTA IS AGAINST THE WALL! SAFETY CAR IS OUT!
That means the end of the race will be a coast and Vettel is set to win a third straight world title.
JENSON BUTTON WINS THE BRAZILIAN GRAND PRIX!
SEBASTIAN VETTEL WINS THE 2012 FORMULA 1 DRIVERS' CHAMPIONSHIP!
It's a tame end to a simply remarkable season-ending race. Vettel is jubilant and the team are in hysterics.
Vettel is told by team principal Christian Horner: "You're a triple world champion!" The German responds with "Oh my god!"
Alonso truly couldn't have done much more this afternoon. He finished on the podium like he needed to but Vettel just about did enough.
Vettel finishes the season on 281 points. Alonso has 278.
Vettel's third straight world title will grab the headlines but let's not take anything away from Button who drove superbly in the wet to claim his third win of the year. He also won the first race in Australia.
Third-placed man Massa is in tears at his home Grand Prix as the British national anthem is played out at Interlagos to acknowledge Button's win.
Let's also not forget Hamilton who, in his last race for McLaren, was cruelly taken out by Hulkenburg.
Schumacher also needs a mention. His fine career in Formula 1 comes to an end with an impressive seventh place finish after four pit stops.
That win for Button moves him into the top five in the standings, nudging ahead of Webber. Raikkonen finished third ahead of Hamilton in fourth.
Vettel is one of the all-time great race drivers but he does seem to get awfully lucky. Alonso has done tremendously to keep pace with the Red Bull man and how Vettel got away with those two early bashes is remarkable.
That was some way to finish what has been yet another gripping season of Formula 1. Vettel is the champion for a third time in a row but he was pushed until the very last lap by Alonso. The 2013 calendar begins in Australia on March 17 and Sports Mole will be ready and waiting! Make sure you continue to check the site for reaction throughout the evening. We'll see you again soon.