Jenson Button claimed his first victory of the season in Canada, beating Sebastian Vettel, who proved he is human by making a mistake on the final lap, having led all the way until then.
It was a chaotic race of five Safety Cars with the race starting behind the SC, re-emerging after a Lewis Hamilton incident, coming back out on Lap 20 for intense rain and then putting in nine more laps when the race was restarted on Lap 25 after a two-hour red-flag delay.
It came out again when Alonso crashed out after tagging Button on Lap 37 and it made its final appearance on Lap 57 so that marshals could clear the debris from Nick Heidfeld's late race shunt.
It was brightening after a long period of rain in Montreal, but with standing water still on the track, the decision was taken to start behind the Safety Car. This meant that everyone had to start on full wet tyres. It also meant that the two DRS zones would not be activated until the race director decided it was safe to do so. The track was only 20C with an ambient of 19C.
Mercedes engineers radioed to Michael Schumacher that rain was expected fifteen minutes into the race. Ferrari's Rob Smedley told Felipe Massa it would be twenty. Jaime Alguersuari opted to start from the pitlane in his Toro Rosso with a full wet set-up. Both McLarens had been given a semi-wet set-up from qualifying.
Grid:1.Vettel, 2.Alonso, 3.Massa, 4.Webber, 5.Hamilton, 6.Rosberg, 7.Button, 8.Schumacher, 9.Heidfeld, 10.Petrov, 11.DiResta, 12.Maldonado, 13.Kobayashi, 14.Sutil
Start: The Safety Car led the field away and so the order remained the same until it came in at the end of Lap 4. Immediately Lewis Hamiltom tried to dive past Mark Webber up the inside into Turn 1 to take P4. Webber left him some room, but Lewis couldn't get his car stopped in time and he spun the Red Bull. Hamilton lost a few places, Webber dropped to P14.
The following lap Jenson Button had a moment after Turn 3 allowing both Schumacher and then Hamilton past him as he lost traction. Hamilton closed rapidly on Michael Schumacher and started to look for ways past him into the Turn 10 hairpin.
Lap 5 Positions: 1. Vettel, 2. Alonso, 3. Massa 4.Rosberg, 5.Schumacher 6.Hamilton, 7.Button, 8.DiResta, 9.Heidfeld, 10.Kobayashi,11.Petrov, 12.Maldonado
On Lap 6 Schumacher had Hamilton alongside him wide on the outside of Turn 10 and almost pushed him off track. The McLaren ran wide and Jenson Button got in front of his team-mate again. Then, at the end of the lap, coming through the final chicane, Button was slow allowing Hamilton to get a run at him down the pit straight.
Hamilton chose to put his car alongside Button where there isn't an overtaking place before the start/finish line and as Button moved across to take the normal racing line, Hamilton hooked his front right behind Jenson's rear left, then bounced into the pitwall.
He dragged a broken rear wheel round the circuit for half a lap until he was told to stop by the McLaren team, who suspected a suspension failure. At the same time a Safety Car was dispatched to recover Hamilton's car and also pick up McLaren debris on the straight.
While all this was happening, Lewis was under investigation on three counts; for his incident with Webber, running too fast behind the Safety Car in the opening stint of the race and then for hitting Jenson. Something must have been awry with the McLaren delta times as Button was also under investigation for running too quickly behind the opening SC.
Button decided to gamble and came in for Inters on Lap 7 behind the Safety Car. As they formed up on Lap 9 the positions were now: 1.Vettel, 2. Alonso, 3. Massa 4.Rosberg, 5.Schumacher 6.Kobayashi 7.Heidfeld, 8.Petrov, 9.Webber, 10.DiResta, 11.Maldonado, 12.Button.
Webber was suffering from an intermitant downshift problem and his engineer advised that they might change a steering wheel during one of the pit-stops. Button was duly called in for a drive-through penalty for exceeding his delta time and served it the moment that the Safety Car came in on Lap 12. It dropped him to P15, but as the track dried out it was clear that the Inters were the tyre to be on.
On Lap 15 Button passed Barrichello, Sutil and Maldonao on one lap. At the front of the race on Lap 16 Vettel now had a 5.5 second gap on Alonso, but Button was two seconds a lap quicker than the leaders and closing rapidly. Such was his pace that Rosberg and Alonso both came in for Inters too.
The race order on lap 18 was now: 1.Vettel, 2. Massa 3. Kobayashi 4.Webber, 5.Alonso, 6.Heidfeld, 7.Petrov, 8.Button 9.DiResta, 10.Rosberg, 11.Schumacher.
Then on Lap 20 the skies opened and it began to pour down with very heavy rain, overwhelming the inters. All those who had changed onto them needed to change back very quickly to full wets. Such was the severity of the downpour that Race Director Charlie Whiting put out a Safety Car.
Alonso and Button retreated to the pits for full wets, while Vettel used the opportunity to change to a new set of wets and still come out in the lead.
Thus as they lined up behind the Safety Car on lap 21 it was all change yet again, the race order now being: 1.Vettel, 2. Kobayashi 3.Massa 4.Heidfeld, 5.Petrov, 6.DiResta.7.Webber, 8.Alonso 9.De la Rosa, 10.Button, 11.Rosberg, 12.Schumacher, 13.Sutil, 14.Alguersuari
As they toured round, cameras switched to the weather radar which revealed that we would have 20 minutes of rain at Intensity 2 and then more at Intensity 1. Leader Sebastian Vettel radioed back from behind the Safety Car that it was undriveable between Turns 9 and 13.
On Lap 25 the Red Flag was waved and the cars came to a halt on the grid, it being too wet to continue. Drivers got out of the cars and waited as marshals struggled to rid the circuit of standing water and the rain continued unabated.
There was a two hour and four minute break while the race director waited for conditions to ease before the cars could get underway again. All were now obliged to change to the full wet tyres. At this stage Lewis Hamilton had been the only casualty, and that of his own haste, not the conditions.
The cars started off again on Lap 26 behind the Safety Car and spent an age touring round. Laps 27,28,29,30,31,32,33 and 34 passed before it was brought in. It had been such a cautious decision that cars were already contemplating changing to Inters before it was withdrawn.
On the restart, Kamui Kobayashi and Felipe Massa fought out a who-will-be bravest duel into the final chicane (not yet with DRS activated) and Turn 1 with Kobayashi holding the place after being very late on the brakes.
Schumacher, Sutil and Barrichello came in for inters at the end of Lap 35. Heidfeld, DiResta and Button a lap later. The lap after that the rest of the front runners - with the exception of Vettel - came in with Ferrari double-stacking Massa and Alonso. Vettel pitted a lap later.
Alonso's delayed stop for tyres had put him back with Jenson Button who was on much hotter tyres and came steaming up the inside of the Ferrari into Turn 3. The McLaren got its nose in front on the inside, but for some reason Alonso thought he could make it through, too. They touched.
Alonso spun gently backwards into the barriers, his car beached on the kerb, while Button limped back to the pits with a puncture and resumed the race plain last. Another Safety Car was dispatched to allow the recovery of Alonso's stricken Ferrari.
The positions as they formed up behind Berndt Maylander's Mercedes SLR were: 1.Vettel, 2.Kobayashi, 3.Massa, 4.Heidfeld, 5.DiResta, 6.Webber, 7.Schumacher, 8.Petrov, 9.Rosberg, 10.Sutil, 11.Barrichello, 12.Maldonado.
Rosberg had lost out to team-mate Michael Schumacher and as Vettel bunched the cars before the restart Adrian Sutil hit him from the rear dislodging part of his front wing.
On Lap 41 we were go again with a racy Michael Schumacher all over the back of Mark Webber. On Lap 42 Mark ran wide at the hairpin and Schumi was through. At the same time Paul DiResta tried a clumsy move on Nick Heidfeld into the final chicane and lost part of his front wing, plus earned a drive-through penalty into the bargain.
By Lap 44 Button had made his way from last place up to P.14. Schumacher was also flying and set a new fastest lap on Lap 45 while driving straight round Nick Heidfeld.
On Lap 46 the DRS zone was enabled. The race order was now: 1.Vettel, 2.Kobayashi, 3.Massa, 4.Schumacher, 5.Heidfeld, 6.Webber, 7.Petrov 8.Barrichello, 9.Rosberg, 10.Maldonado, 11.Alguersuari, 12.Button.Schumacher was now just 10 seconds off the lead. On Lap 49 Button passed Maldonado and Alguersuari for P10. A lap later and Mark Webber was one of the first to go for slick tyres. He began to set personal best sector times and so Button followed him in for slicks a lap later. It was his sixth trip down the pitlane during the race.
On the same lap Michael Schumacher came up to the back of the battle for second and third place between Kobayashi and Massa. The Japanese driver ran wide in Turn 5, covered the line and slowed Felipe Massa down to prevent him overtaking and then Michael Schumacher swept by them both. From P4 to P2 in one easy move. Massa took P3.
On lap 52 both Schumacher and Massa pitted for slicks and rejoined in the same positions, except now Michael had some backmarkers in between himself and Massa. When Massa tried to go round one and off the dry racing line, he lost control and slewed his nose into the wall dislodging it. He had to race back to the pits to change it and rejoined in P12.
At this stage Mark Webber and Jenson Button were both charging hard, Mark Webber's progress was halted when he came up behind Schumacher.
The order on Lap 54 was; 1.Vettel, 2.Schumacher, 3.Webber, 4.Kobayashi, 5.Button, 6.Heidfeld, 7.Petrov, 8.Barrichello, 9.Alguersuari, 10.Rosberg.
Button was reducing the fastest lap by chunks and on lap 55 he was easily up into P4. Kamui Kobayashi was falling back very quickly and a lap later Nick Heidfeld had so much more traction in Turn 2 that he simply drove into the back of the faltering Sauber.
This broke Heidfeld's front wing and as he ran towards Turn 3 it broke in front of him and he was launched over the top of it and into the escape road. There was so much debris on the track that the Safety Car had to come out yet again on Lap 57. This closed the cars up with a race order of: 1.Vettel, 2.Schumacher, 3.Webber, 4. Button, 5.Kobayashi, 6.Petrov, 7.Barrichello, 8.Alguersuari, 9.Rosberg, 10.Maldonado, 11.Massa.
Vettel escaped after the restart yet again and looked to be disappearing up the road to leave the real fight between Schumacher, Webber and Button for the remaining two podium places. Petrov was soon past Kobayashi as Massa started to pick off places further back.
On Lap 63 Mark Webber managed to pass Michael Schumacher on the back straight but cut the chicane in the process and had to give the place back. He managed to do so without allowing Button through. A lap later and Webber cut the chicane again, but as he rejoined the track, lost traction on the wet, fishtailed and allowed Button through into P3.
Button was flying and on Lap 65 he passed Michael Schumacher into the final chicane, quite easily thanks to the DRS and set the fastest lap of the race to boot. With five laps to go he was just 3.1 behind Vettel, who was 1.5 seconds a lap slower.
Vettel had to ratchet up his engine mode as the gap between the Mclaren and the Red Bull reduced. On Lap 67 (out of 70) his lead was just 1.3 seconds. The race was close to running over the two-hour mark, but there was just enough time to run all the laps. Mark Webber eased his way past Schumi on Lap 67 and the dream of a podium for Michael was over.
Vettel was now just about matching Button's sector times, but the McLaren was getting ever closer. On the final lap it looked as though Jenson would be close enough to use the DRS down the final back straight, but heading towards Turn 5 Vettel cracked under pressure, ran wide and allowed the Mclaren through.
Button surged through to take the win on the last lap. Vettel had led every lap until the very last one. Webber lost time and only just finished ahead of Schumi in P4 with Petrov finishing fifth and a recovering Felipe Massa passing Kamui Kobayashi with centimetres to spare for P6 at the flag.
It had been an epic race over an enormous period of time. Red Bull had failed to win in Canada yet again, but Vettel had increased his lead in the Championship to the point where he is almost three wins ahead of his nearest rival.
Ferrari had started in P2 and P3 and finished with a P6. But it was Button's day and he had at last proved that if you put Vettel under enough pressure he will make mistakes.
01. Button McLaren-Mercedes 1h23:50.995
02. Vettel Red Bull-Renault + 2.709
03. Webber Red Bull-Renault + 13.828
04. Schumacher Mercedes + 14.219
05. Petrov Renault + 20.395
06. Massa Ferrari + 33.225
07. Kobayashi Sauber-Ferrari + 33.270
08. Alguersuari Toro Rosso-Ferrari + 35.964
09. Barrichello Williams-Cosworth + 45.100
10. Buemi Toro Rosso-Ferrari + 47.000
11. Rosberg Mercedes + 50.400
12. de la Rosa Sauber-Ferrari + 1:03.600
13. Liuzzi HRT-Cosworth + 1 lap
14. Karthikeyan HRT-Cosworth + 1 lap
15. D'Ambrosio Virgin-Cosworth + 1 lap
16. Glock Virgin-Cosworth + 1 lap
17. Trulli Lotus-Renault + 1 lap
18. Di Resta Force India-Mercedes + 3 laps
Did Not Finish
Maldonado Williams-Cosworth 62
Heidfeld Renault 57
Sutil Force India-Mercedes 50
Alonso Ferrari 44
Kovalainen Lotus-Renault 36
Hamilton McLaren-Mercedes 8