Stewart says Di Resta should start down grid

Di Resta, 23, will be Force India's test and reserve driver this season, having previously starred in Formula 3 and German touring car racing.

The Scot may have to bide his time before making his Grand Prix debut and when he does so, it will be for a team not expected to challenge at the front of the grid.

That is in stark contrast to the career path of Hamilton, who was fast-tracked into F1 by McLaren, while current world champion Button spent years in the wilderness at BAR and Honda before clinching the title last year.

Alonso, however, started at the very bottom with Minardi in 2001 but shone to such an extent that he found himself at Renault a year later. The Spaniard soon became the sport's youngest-ever world champion and Stewart believes, like Alonso, Di Resta must take full advantage of any chance he gets. "Alonso came in with Minardi; nobody was going to win in a Minardi," Stewart said. "But the guys saw that he had what it took."

Asked if he felt the same about Di Resta, three-time world champion Stewart said: "It's not something that you can forecast that easily. He's got to get in there and, at the end of the day, has got to deliver.

"It's too early to ask that of him. He has to get in a car and he has to get regular starts. Then, you're going to judge him, first against his own team-mate." He added: "There's no doubt that it's hard work; it's focus, it's commitment, it's dedication, it's sacrifice. It's all the things that any top sportsman needs to do in order to get to that level."

Stewart, 70, is Scotland's last F1 world champion, his most recent title coming 37 years ago. But he insisted his country was punching above its weight in motor sport, pointing to recent successes in IndyCar, Le Mans and rallying.

"We've done very well; Scotland's been extraordinarily rich," he said. "We've had Scots waving the flag now for so many years.