'Unless you're Ferrari, most team principals would never admit to being optimistic' The first thing Sir Frank Williams asks me when I walk into his office at the Williams Formula One compound at Grove, near Wantage in Oxfordshire, is to explain the political hue of The Independent. There is no need for me to put the same question to him. A large portrait of Margaret Thatcher on the wall behind me rather advertises his colours. "I was a big fan; I think that in some areas she created necessary and pivotal change," he says.

He gives interviews sparingly, which is a shame, for he is an urbane and articulate man, and an impressive cheerleader for Formula One. His team's acutely disappointing season in 2006 - a hapless eighth in the constructors' championship, the worst performance since 1978 - has not shaken his enthusiasm for the sport one jot. If anything, he says, his enthusiasm has intensified.

But enthusiasm does not translate into optimism. "Unless you're Ferrari, most team principals would never admit to being optimistic," he says, smiling. "Certainly, we are hopeful of improving ourselves. We know we must, and I think we will. I believe we've got a much more serious racing car now."

That much appears to be true. After being effectively sacked by BMW, the team last season used a Cosworth V8 engine, but now have the more powerful Toyota on board. Moreover, the boss himself has a formidable record in overcoming adversity. So, with the 2007 season about to get under way, does he think AT&T Williams, as it is now known, will ever again win a grand prix? Is first place on the podium - and it has happened a whopping 112 times since Clay Regazzoni's inaugural win for Williams in 1979 - achievable once more? There is a slightly disconcerting silence while he mulls over the question. "It is certainly possible," he says finally. "I'll have a better answer for you in six months' time."

And if the answer is a negative one? If Williams have another dreadful season, how long can he justify and sustain under-achievement in what is a ruinously expensive business? "Oh, we'll survive for a long time yet, but it is not acceptable as a credo for Patrick and myself to be happy with the way things are."

Patrick is his director of engineering and the team's co-owner, Patrick Head, whose virtues Williams lists with what might almost be described as ardour. "Meeting Patrick is the most significant thing that has happened to me in the last 35 years, apart from getting married," he says. "We formed a partnership which is this business, and because of his brilliant mechanical engineering, his understanding, his hard work, his dedication, his powers of reason and his intellect, we have put this company on the map. He is an outstanding man, and his main task has been to steer me away from the mistakes I make. In the early days every day was a technical disaster of my own making. Patrick rescued me from my own technical follies."

Williams' modesty becomes him, but seems curiously at odds with a sport that is propelled by egos as much as engines. After all, he has given his name to what amounts to a small empire; even the roundabout on the A338, just outside the compound, is named after him. So I ask whether he has ever been in Formula One for the ego trip?

"I'm highly competitive, so of course there is ego involved." OK, nice answer. Let me ask another teaser. Having listed Head's many assets, what does he consider to be his own? Another long pause. "I have an ability to get along with people, to turn the other cheek, to take the rough with the smooth."

There have certainly been some rough passages along the way, not least the death of Ayrton Senna in a Williams car, at Imola almost 13 years ago. Did that tragedy - after which Williams and two of his engineers were charged with manslaughter by the Italian authorities - change his life?

"Truthfully, no. But it hurt a lot." And is it true that, although the charges were dropped, the legal case against him is still going on? "Technically yes, but functionally it is closed. There is no chance of anyone from Williams finding themselves in trouble with the law in Italy."

Senna's death, he adds, was at least not in vain in terms of safety. He praises Max Mosley, president of world motor sport's governing body, the FIA, for acting swiftly to make cars and circuits safer, and although he has had his run-ins with Mosley, adds further praise for the way Mosley is seeking to make - it seems like an oxymoron - Formula One greener.

"Max understands that unless we act cleverly, ahead of the pack, we'll be under attack, so in its development of the internal combustion engine, F1 is moving in an eco-friendly direction. Stand by for some interesting new engine technology, with which all manufacturers want to be involved. The rate of development that occurs in terms of horsepower gains, fuel efficiency gains, is very, very quick. If you compare the aircraft industry; the Eurofighter had its first demo in 1986 and only entered service about three years ago. Almost 20 years! We take six months."

So the headline on this piece should be that Formula One is saving the planet? An obliging smile. "No, but it wants to play a part."

And what does he say to the charge levelled by his fellow knight Sir Stirling Moss, among others, that with the cars becoming almost mobile computers, the skill required by drivers has diminished in Formula One?

"I would say the opposite. But it's true that we have a lot of engineers here, I won't tell you how many. None of them are a waste of money."

However many there are, and however much they cost, he has come a remarkably long way since the day almost 50 years ago when a wealthy Glaswegian went to visit his nephew at a Scottish boarding school, and offered to take nephew and friend - young Frank Williams - out for a spin in his grey Jaguar XK150S.

"Jaguar had just won Le Mans for three years in a row, and the ride was the thrill of my young life. Top down, no seat belts, 90mph along tiny roads in Dumfriesshire." He doesn't need his many engineers to make him a tardis, to be transported back in time. "It was very quick."

When he left school, Williams paid £50 for an old saloon racing car once owned by Graham Hill, and joined the merry gang of adventurous young men who toured the Continent every summer looking for races. Again, an expression verging on rapture flits across his face at the very memory. "That was a great existence, going from race to race, stopping for breakfast on the old Autobahns. Just brilliant."

In 1966, aged 24, he founded Frank Williams Racing Cars, which put him in pole position, or at least on the grid, when Bernie Ecclestone created Formula One as we now know it. How does he get on with Bernie?

"I'd like to say very, very well indeed. Bernie is truly an enigma, although I've known him since 1969, and he walks in a straight line, speaks in a straight line. You know exactly where you stand, and if you cross him, you can consider yourself in serious trouble. Having an argument with him is healthy, he respects that, but if you cross him..."

It sounds as though he speaks from grim experience, but he insists not. Is it unequivocally good for a sport, though, to have one man as powerful as Ecclestone running things? "Well, we're all aware that Bernie wants to make it more and more global, so stand by for more races, maybe 20, or maybe he'll push for even more, and a long way from England. Do I disapprove? No. It's the future. We have to go where the money is. I'm happy. And what Bernie has done is remarkable, getting F1 to where it is, compared with where it was."

Apart from Ecclestone, and members of his own team, Williams adds that he cannot claim to be close to anyone in Formula One. "There are several other team principals like Ron Dennis with whom we have common principles, generally speaking, but that's all."

Maybe the competition is simply too intense; it's certainly not as though race days offer much chance to socialise. "There is so much to worry about," he says. "Will the car finish, have we put the right amount of fuel in, when will the others make their first pit stop, will the car get away cleanly at the start, survive the first corner? A million things can go wrong. I can't ever relax."

On Sunday in Melbourne relaxation will be in shorter supply than ever, as the car, with its new engine, feels the heat of competition for the first time. And benign as Williams is today, he can also reportedly be an uncompromising taskmaster. So there will be pressure all round, perhaps above all on his new driver Alexander Wurz, the 33-year-old Austrian promoted from test driver to succeed Mark Webber, who has moved to Red Bull.

But the boss has high hopes. "He [Wurz] is very popular in this building. He's a gentleman, who gives a lot of his time to the people who design and make the cars. He's very inclusive, a very good communicator, a pleasure to have on the team. And technically he's extremely useful. He understands racing cars, and when he leaves the track after testing or racing he leaves a great deal of analysis. Multi-page e-mails are de rigueur, and hopefully that rigour will pass to his team-mate Nico [Rosberg]."

Meaning that Rosberg - the 21-year-old son of Keke Rosberg, who won the world championship with Williams in 1982 - is less helpful, less responsible? Williams smiles. He's not about to rubbish his drivers to me. "He's still very young, but he's very bright."

However good Rosberg turns out to be, and however well Wurz does, it's safe to say that neither of them will ever thrill Williams like Senna did. When I ask him to pick out the finest bit of driving he has ever seen, he does not hesitate. Nor would anyone who was at Donington Park for the European Grand Prix in May 1993 when the Brazilian, entering what would be the last year of his life, and driving an underpowered McLaren, screamed round a wet circuit making the likes of Alain Prost look like beginners.

"It was an almost exaggerated demonstration of superiority," Williams recalls. "He demolished everybody, went from sixth to first in the first two corners, and lapped everybody at least twice. It was spectacular."

He sounds awestruck even now, perhaps as awestruck as he was in the Jag thundering along the lanes of Dumfriesshire half a century ago. And maybe that is the essence of Sir Frank Williams. He remains at heart an impressionable schoolboy in thrall to speed and power.

As I leave I ask him about the model of a jet that he has on the sideboard in his office, and he gets talking about the F-22 Raptor, the American fighter plane. I am reminded of my sons playing Top Trumps.

"It's got a brilliant electronic suite for enemy detection," he says. "It brings down the enemy 120 nautical miles way." His eyes shine. "Phenomenal, absolutely phenomenal."