Sometimes a chance remark can change the course of history.

When Fernando Alonso stood on the Brazilian Grand Prix podium last year, soaking up the adulation of his jubilant Renault team on what he called the greatest day of his life, the world saw a 24-year-old confirmed as Formula One's youngest champion.

What even those closest to the Spaniard little suspected was that even in that very moment of triumph, even as he gave his post-race interviews with the champagne still wet on his overalls and the cheers ringing in his ears, he had set in motion a shock move to McLaren in 2007.

Exactly how that coup came about has been cloaked in mystery since the news burst like a bombshell on an unsuspecting Formula One last December.

Alonso has been coy about the details, saying only that he negotiated the switch himself while keeping team manager Flavio Briatore in the dark.

He has hinted at concern about Renault's long-term commitment to the sport while others have focused on the financial rewards.

This week, McLaren head Ron Dennis filled in some of the background with a version of events that highlighted how a casual compliment turned into something momentous.

"We all thought the door (to Alonso) was firmly locked," he told reporters on Wednesday. "The point where it became apparent that it was very clearly not locked was on the podium of the 2005 Brazilian Grand Prix."

GREAT SECRECY

"We had come first and second with our guys, they were hot and sticky and wiping themselves down around the back and drinking water," continued Dennis, whose team had been celebrating their first one-two in more than five years.

"He (Alonso), having come third, was obviously very keen to get the whole thing over with even though he had won the championship.

"It was one of those moments where we were alone for about a minute or something.

"I might have said 'congratulations on the world championship' or something. And his response was along the lines of 'Well, the thing about you guys is that you make it so difficult because you keep developing your cars'.

"I said 'You could be part of it'.

"And he just said 'I'd like to be'. I was just stunned. I said 'Are you serious?' and he said 'Yes'."

The two met in great secrecy in a hotel room at the following Japanese Grand Prix and, three weeks after the initial conversation, the deal was done.

Since then, Alonso has gone on to win his second championship with Renault while Kimi Raikkonen has left McLaren for Ferrari.

There can be little doubt that McLaren feel they have got the right man for the job, a driver with the potential to rank alongside the all-time greats.

The team knew Alonso was good when they snapped him up. After last season, they suspect he could be even better than they thought.

"Fernando, I'm sure, will be phenomenal," said chief executive Martin Whitmarsh.

"From the moment that we decided to pursue Fernando, which from my recollection is slightly different to Ron's, we thought it was the right thing.

"We thought we made the right decision a year ago, but it was actually a better decision than we realised at the time.

"This year I think he has had a much more difficult political environment.

"When you take on Ferrari, you take on City Hall as well.

"He had several setbacks this year, in terms of stewards decisions," added Whitmarsh. "And he has demonstrated just how battle-hardened he is."

NO EXCUSES

McLaren failed to win a race last year for the first time in a decade, after winning more than Renault the previous season, and there can be no excuses in 2007.

With Ferrari's Michael Schumacher now retired and Canadian Jacques Villeneuve forced out, McLaren have the only world champion on the starting grid.

"If we are not winning next year, we cannot say our driver lineup is not good enough to do it. It clearly is," said Whitmarsh.

"By reputation and by experience, Fernando is very consistent and does his best against all the odds. He has all the Schumacher-esque qualities about him. And therefore there is no hiding."