The warm smiles and handshakes that world champion Jenson Button and Lewis Hamilton will regularly exchange next season are bound to suggest that the two McLaren drivers remain the best of friends.

But Button, who today finally completed his move from Brawn GP to the Woking team, had better beware. Because every time Hamilton passes his new partner's car in the pit lane or the garage, that No1 on the nose cone will be like a red rag to a bull.

Nothing else will motivate Hamilton more than the constant numerical reminder that in world championship status, at least, he is secondary to his British compatriot.

Will Button come to regret teaming up with one of the fiercest competitors on the grid rather than remaining king of the castle at Brawn, relaunched this week as Mercedes Grand Prix?

That will be one of the most intriguing questions of the 2010 season and Sir Jackie Stewart has already offered his own answer.

“It is a mistake,” said the three-times world champion today. “Jenson is walking into the lion's den.”

Stewart revealed how, back in 1965, he was offered a seat at Lotus alongside fellow Scot Jim Clark. But he turned it down because Lotus was built around Clark, who had been given his big chance in Formula One by Colin Chapman's team and went on to win two titles with them.

Stewart believes Hamilton is McLaren's Clark and Button is bound to feel the outsider there, whatever assurances he has been given by team principal Martin Whitmarsh that the two men will receive equal equipment and treatment.

Stewart said: “If I had been Jenson I would have wanted to do a deal with Brawn because I know the culture of the Brawn team. I have a high respect for Ross Brawn and I know the mechanics there respect Button.

“There is a totally different culture in McLaren, something he might never have experienced. They have a very clinical culture which doesn't have the emotion or drive in the same passionate way Brawn would have had with Jenson in there as world champion. But I do believe the McLaren car next season will be one of, if not the, best car on the grid. So therefore he is going to with a team that wants to succeed.“

Stewart believes Button should take heed of the experiences of Fernando Alonso, who left McLaren at the end of 2007 after a troubled year alongside Hamilton. Stewart said: “It will be difficult for Button to take on Hamilton. He has had three years driving for McLaren, he has it shaped his way and he has already exposed one driver who came in there.

“Alonso couldn't cut it against Hamilton and I think that Lewis will want to retain his position of prominence in that team. He will be a tough guy for Jenson to marry into.

“At Brawn, though, he would have had an advantage of being with a team he's driven with for a number of years. Nico Rosberg would have been his team-mate and I think Jenson would have had an advantage over Rosberg.

“There is a record within McLaren of them having two top drivers. Alain Prost and Niki Lauda were together there, and Prost and Ayrton Senna were together there.

“That last one was a very acrimonious relationship within the team and I don't believe the team dealt with that in the very best way because of the culture of the team.

“Having said that, few teams other than McLaren would have taken on two drivers of that calibre, head-to-head, who were constantly trying to win.

“When Juan Manuel Fangio and Stirling Moss drove together for Mercedes in the Fifties there was only one No1 — Fangio. Stirling was his No2 and admired him enormously.

“What we're looking at today is two guys that want to be No1. That in one team doesn't make for perfect bed partners. There will be differences.”

Former team owner Eddie Jordan claimed the Mercedes takeover of Brawn, winners last year of both the drivers' and constructors' titles, meant the new team was always going to have a German bias — German drivers Rosberg and Nick Heidfeld are now expected to be confirmed as their championship challengers in 2010.

Jordan said: “I'd like to have seen Jenson defend his title in the Brawn team, which gave him the chance to be champion.”

Unlike Stewart, however, Jordan, now a pundit for the BBC, believes Button can rise to the challenge of Hamilton. He said: “It will be a mouthwatering prospect, watching them both.

“On one hand you have the team that was built for Hamilton and it's clear that the whole McLaren team are behind him. However, Jenson will bring a different feeling to the position and if any team was capable of being able to handle these egos and talent, then McLaren are that team.”