When Hamilton pitted from the lead on lap 50 for a new set of soft tyres, his McLaren team was convinced their rivals — second-placed Fernando Alonso and third-placed Sebastian Vettel — would follow suit and stop again.
Instead, they stayed out and Hamilton had to push hard to recover, eventually making the most of his fresh rubber to overhaul the drivers in front of him and regain the lead.
In truth, though, McLaren were confident they had it covered whatever their rivals chose to do.
Hamilton's pace on the soft tyres after his first stop on lap 17 was impressive. He was consistently between 0.2s and 0.6s per lap faster than second-placed Alonso (who stopped on lap 19) for most of the second stint, with the Ferrari faster than the McLaren on just three occasions. Against Vettel, who stopped on lap 16, he was around 0.6s faster per lap on average early on in the stint.
The difference in pace levelled off a little in the middle of the stint but in the two laps before he stopped, Hamilton was beginning to become slower than both. For McLaren, there was little question that they needed to stop — but as they proved they didn't necessarily need their rivals to do the same.
With Hamilton clearly demonstrating at the start of the first stint that he was at an advantage when all were on fresh tyres, he would almost certainly have had the pace to get by if they had all stopped. The question was more whether he had the pace to chase them down if they didn't — and that was all down to the calculations.
The extra weight of 10kg of fuel in Canada is effective to around 0.28s of lap time increase, and cars were using around 2kg of fuel per lap. Comparing the relative fuel-balanced pace on lap 20 with the pace on lap 45 shows the actual effect of the tyres.
In theory, 25 laps should need 50 kg of fuel, which equates to 1.4s difference in lap time.
In the early part of the stint, Hamilton was averaging around 1m19.1s. Taking off the 1.4s fuel effect to enable comparison with times set around lap 45, that equates to 1m17.7s pace. On lap 45, Hamilton was averaging around 1m18.2s — so on that calculation it appears tyre degradation was costing him around 0.5s.
In contrast, Alonso averaged 1m19.5s in the early part of the stint, which equates to 1m18.1s on lap 45 fuel loads. In the latter part, he was running at around 1m18.1s - suggesting his tyres had not yet begun to suffer. Similarly, Vettel was also relatively unaffected by tyre wear at that point.
What was clear, however, was that Hamilton would be around a second per lap quicker than his rivals once he had stopped and their tyres began to wear, and that advantage would only grow as they started to suffer greater degradation as the race came to an end.
And sure enough, that is exactly what happened.
Hamilton was immediately a second faster than Alonso, who chose not to stop, and by lap 60 that was more like 1.6s faster. The same was true of Vettel, until he chose to stop with seven laps remaining for a fresh set of tyres himself.
It was not a genius strategy from McLaren — the second stop was just simply what Hamilton needed to do to avoid dropping like a stone. Stopping was the only way he was going to have a chance of winning.
It proved to be the best solution, but the tight field and the late changes in the race showed there was little difference between a wide variety of strategy options — as the top five all took a slightly different approach.
Hamilton's two-stopper took victory with 16 laps on super softs followed by 33 laps on the first set of softs and 20 laps on the second set.
But rather than his mid-race rivals Alonso and Vettel following home behind it was the Renault of Romain Grosjean which made a burst into second.
Grosjean nurtured his tyres to overhaul the drivers in front as he made a one-stop stick, with 21 laps on super soft followed by a massive 49 on soft tyres.
Sergio Perez also made the one-stop work, starting on softs (from 15th on the grid) and running 41 laps on those (on heavier fuel) followed by a carefully-managed 29 laps on the super softs to take third.
Fourth-placed Vettel ran initially the same as Hamilton, starting on super softs then switching to softs after 16 laps. But his plan to make the softs last 54 laps was a over-ambitious and when his tyres ran out of grip after 47 laps he put on a set of super softs for the seven laps to the end.
That allowed him to jump Alonso, who elected to persist with his fading tyres and stay out, ultimately running 51 laps on the soft tyres — a decision that Ferrari has backed despite losing a place to Vettel in the end.
After the race, Alonso made a good point: "If I stopped behind Hamilton I would finish second behind Hamilton, but if I had the degradation of Grosjean, I would have won the race, Vettel would have been second, Grosjean third and Hamilton fourth - and now you [the media] would be in the McLaren garage saying two-stop is the wrong strategy."
It all shows that the toughest part of F1 in 2012 is not in the car, it's on the pit wall.