Frank Williams's still got the drive as he reaches milestone

Despite being confined to a wheelchair, the result of a car accident 22 years ago, he has been undertaking a familiar routine of fussing over his drivers, holding technical briefings with engineers and talking big money with his team's blue chip sponsors.

A man whose face rarely betrays emotion, Williams regards the fact that the sixth round of this season's world championship marks a record 600th grand prix as a team entrant as no more than a statistic. "As most people would expect, reaching 600 grands prix means very little to me," he said.

Yet the landmark is being celebrated by many of those who have driven for, or worked alongside, a remarkable man who once conducted business from a public phone box but who now figures in the Sunday Times Rich List with a fortune estimated at £79million.

During the course of Williams's four decades in motor sport his cars have won 113 grands prix, seven drivers' world championships and nine constructors' titles. It is an amazing record and one the 66-year-old acknowledged when he let that mask of inscrutability slip for a moment.

"I have to admit that there have been some brilliant moments over the 40 years that I've been racing," he said. "There have also been some moments of great sadness."

Two black and white photographs dominate the stark white walls of his office at the team's Berkshire headquarters.

One is of former friend and flatmate Piers Courage, killed driving for Williams in the 1970 Dutch Grand Prix. The other of Ayrton Senna, the Brazilian legend who died behind the wheel of a Williams at Imola 14 years ago. The loss of both men hit Williams hard. But the restricting legacy of his own crash has probably had a more profound effect.

His partner, Patrick Head, said: "Frank first employed me in November 1975, since when I haven't seen much change in him except for the physical changes as a result of his accident in 1986.

"When we first started working together I suppose you could say he was a bit like Tigger of Winnie the Pooh fame, full of enthusiasm and excitement. Since his accident he's become a deeper thinker and much more strategic. But I think that has benefited the team."

Australian Alan Jones, who won Williams's first world title in 1980, said: "Frank's resilience, and his energy and enthusiasm, have never ceased to amaze me. Most people would have run out of steam."

In a sport increasingly dulled by constraints imposed by corporate involvement, Williams retains an essential individualism. Keke Rosberg, a world champion with the team in 1982, said: "Frank's situation is unique because he really is the last team principal who goes motor racing for its true essence and that's to race."

Rosberg's son, Nico, now drives for Williams and typically it will be his performance in Sunday's race - yesterday afternoon the promising young German was second fastest in practice behind Britain's Lewis Hamilton - that will be the only thing of interest to the team owner. "I'm very proud of our successes," said Williams. "But I don't dwell on the past. I'm always looking ahead."