Just why has Button become undone?

Sky Sports F1's Mark Hughes explains why Friday's gearbox failure caused Jenson Button's weekend in Canada to spiral into disaster. But the question of why the McLaren driver's season started to unravel as long ago as Spain is an ongoing mystery...

Montreal 2011 was probably Jenson Button's greatest drive. Montreal 2012 was possibly his worst. The only driver with such severe tyre degradation that he was forced to three-stop, Button came home a disastrous 16th, lapped by his winning team-mate Lewis Hamilton. He came into the weekend determined to put a line under his recent woes, but they only worsened. In Monaco, after failing to reach Q3 for the second successive time, he said: "I'm clearly doing something wrong, either in my driving or set-up choices, and I need to find out what it is quickly, because I'm losing points here." He decided he was going to take a new-broom approach to the Montreal weekend and had the team remove a key piece of what is described as 'electronic trickery' that had been on both cars all season. The team is very secretive about what it might be, but Jenson felt that the system may have been confusing his senses in the feedback he was getting from the car, and that this may have been causing him to make poor set-up choices. For Montreal he would get back to basics and he also decided to forgo the new Montreal-specific rear suspension that would be fitted to Hamilton's car, which had less anti-squat built into its geometry. This would allow the Hamilton car to squat (under acceleration) and dive (under braking) a little more, mainly for the benefit of traction. But it would also mean the car wouldn't be kept in as tightly-defined a ride height window, with potential resultant aerodynamic losses. Deciding not to go into the weekend with two new variables, Jenson began Friday practice with the conventional suspension and the 'electronic trickery' removed. However, his running was curtailed part-way through P1 - before he'd been able to get any long-run tyre data - by a gearbox bearing problem that damaged a seal and allowed oil to leak onto the clutch. At first it was believed to be just a failed seal and the seal was replaced ready for the next session. But only after it was started up and the oil leak was still there was it revealed the damaged bearing was causing the seals to fail - so the gearbox had to be removed yet again. At this point, still trying to get Button out for some of P2, McLaren began fitting a spare gearbox, but this was of a different specification, like Hamilton's, with a casing designed for the pick-up points of the new rear suspension. Had this been fitted in time Button would thereby have been forced to run with the Hamilton-spec suspension. Instead they ran out of time, Button got no meaningful P2 running and overnight the team fixed Button's original gearbox and had it back on the car for Saturday and Sunday. Had Button not had the problem, he'd have likely discovered during the Friday long runs that his chosen set-up was excessively hard on the left-rear tyre. Instead, this was only discovered in the race. Jenson had a car that struggled to switch its front tyres on, giving him understeer into the corners, but which then gripped mid-corner, inducing the rear into oversteer on corner exits. This destroyed the rears. So it can be appreciated that whilst a gearbox problem is never good, the timing of this one was disastrous, for it prevented Button from discovering how his new set-up behaved over a race stint - and that it wasn't simply a case of using his team-mate's data to catch up on lost time, because he was using a fundamentally different set-up to