Sometimes you can tell a lot about a driver's demeanour when he is really under pressure.
In Jenson Button's case, as he could become Britain's 10th world champion here in Interlagos this weekend, there are two tell-tales. He smiles a lot, and he plays things down. It's a habitual trait.
Actually, Button has been smiling most of the year, ever since six victories in the first seven races made the title seem like a slamdunk for the man who had been all but written off after seasons from hell with uncompetitive Honda machinery.
Back then, he seemed so invincible that everyone else was racing for second place. Even when Sebastian Vettel and Mark Webber in their Red Bulls beat him in the rain in China in the third race, he got straight back on track in Bahrain and Spain, and grabbed the lead from the upstart German on the opening lap in Turkey just to put him in his place.
Things began to go wrong after that, as Red Bull hit a purple patch and Rubens Barrichello started to get a better handle on setting up the tricky Brawn he shares as Button's team-mate. Since that Turkish Grand Prix, Button has rarely looked a winner, while Barrichello and Vettel have each won twice.
Now it has come down to a two-race scrap, though six points — third place — here for Button could settle the issue on Sunday, a fortnight before the inaugural race in Abu Dhabi. Button has the odds in his favour with 85 points to Barrichello's 71 and Vettel's 69.
If he should stumble at this late stage, as fellow countryman Lewis Hamilton did in 2007 when his own 17-point cushion was eroded by Ferrari's Kimi Raikkonen in the last two races, Button will forever have to live with the ignominy of being branded just another British hopeful who wasn't quite good enough.
Yet despite that pressure, he said: “I feel good, not least because a Virgin bash has been organised next Tuesday evening in London, just in case. The last time I had to rush away from a really important race result was when I had to fly to Tokyo for Honda in August 2006.” Immediately after he won his first grand prix, in Hungary.
So Button, coming up for 30 in January, continues to smile, and to play down expectations: “Sure, I'm gonna wrap it up this weekend, no problem.”
Vettel, meanwhile, is free to push for the victories and to hell with the consequences.
“Sebastian saying the pressure is on us is not quite the case, it's the same for all of us,” he pointed out. “We're all fighting for the championship, it's the first time for me, Sebastian and maybe Rubens. It's an exciting situation to be in, but I'm the one with the lead. We're all fighting for something that is far greater than we have achieved in the past. I don't think it adds to the pressure knowing that you could win the world championship, but it adds to the excitement for sure. I am positive.”
Barring disaster, Brawn will wrap up the world championship for constructors this weekend so long as one of their drivers finishes at least eighth, for all they need after a dream season is half a point over Red Bull to throw things beyond their reach.
“It's an amazing story and it is a Hollywood movie, if it happens,” Button said of that side of the tale. “It's not certain yet. I think the team have been through a lot. It was a difficult situation over the winter, a lot of them found it tough, but in the end we got the deal done and were able to come racing. If we come away with the constructors' in the first season of Brawn GP, it will be a very emotional moment for everyone, as it was in Australia when we finished 1-2. It was the first time I've seen Ross [Brawn] speechless and if it happens here or Abu Dhabi it will be the same.”