Formula One rookie Lewis Hamilton may have only a few months to prove himself at McLaren before the critics start to sharpen their knives, according to Britain's last champion Damon Hill.

Hill, a winner with Williams in 1996, ran the rule over his country's four grand prix drivers at the Autosport International show on Thursday.

He said Hamilton, 22-year-old team mate to double world champion Fernando Alonso, and Honda's Jenson Button were the men to watch.

"It's very plausible that he (Hamilton) will get a grand prix win during the season," Hill told the audience, while warning that the McLaren youngster had to assert himself as soon as possible.

"You've got a season's grace I think, maybe even half a season's grace," he said.

"Maybe people will give him the leeway and the benefit of the doubt for that first six months but then, at the end of the season if he hasn't outpaced Fernando at some point or other, people will say 'Where is it, where's the spark?'

"Drivers who have gone on to become great like Michael Schumacher, Alain Prost and Ayrton Senna arrived and went bang. They were on the scene, on the pace, outpacing their team mate, there right from the word go," said Hill.

PROTECTIVE SHIELD

Hill, who partnered Prost at Williams in 1993 and then Senna in 1994 until the Brazilian's death at Imola, said Hamilton would have something of a 'protective shield' at first.

"He's got a window of opportunity to learn, but it's going to be a short one," said Hill.

"It's a wonderful gift for Lewis to be put in a team with a guy like Fernando. All he has to do is beat Fernando and by definition he's a potential two times world champion.

Hill said Button, who took his first grand prix win in Hungary last August, was a much stronger driver than the appearances suggested.

"This year has to be the best chance we've had since I won the championship for there to be another British world champion," he said.

"I have great faith in Jenson. I think he has a whole team around him so you can compare his position quite well to that of Michael Schumacher at Ferrari...He's got a very good chance of winning on a regular basis."

Red Bull's David Coulthard, now the oldest man on the starting grid at 35, and 27-year-old Anthony Davidson at Super Aguri are the other two British drivers.

"He (Coulthard) can win grands prix but maybe that window of opportunity (for the title) has passed David by," he said.

"But you can't say that for sure, because it's happened in the past that drivers have suddenly found themselves well-placed in a competitive car," added Hill, himself a champion at 36.

"He's still young enough to convert that into a championship given the chance."

Hill added that his money was on Kimi Raikkonen, Schumacher's replacement at Ferrari, to win the championship.