HOW DO you prepare to meet Max Mosley? For so many years the smartly besuited head of global motorsport, now one of the world's most famous fans of sadomasochism. He still runs motor racing, but his reputation has changed rather a lot. Still the same man, but a very different aura.

So what do you say? "Hey Max, I haven't seen you since I watched you talking about your sex life in the High Court"? Perhaps a little blunt. Or "Hey Max, other than the public humiliation, how was your summer"? A little naive. And then, as I ponder this, he's there, offering a handshake and a smile, and looking, well, completely normal.

This is the first time Mosley has done a sit-down interview since the end of his court case against the News of the World. He was victorious, winning £60,000 in damages after disproving allegations of indulging in Nazi role-play, but his victory came at a price that many would have been unwilling to accept.

In court, under cross-examination, he admitted to a passion for S&M sex that has gone on for decades. In fact it's been going on throughout his adult life, despite the fact that he's been married for very nearly 50 years, a trail of deception that staggers most people who hear about it.

Just imagine that for a moment. Imagine spending five decades with the same partner, and yet, for all that time, concealing a secret that you know would break their heart. And then imagine talking about it in front of a packed court room, in the certain knowledge that it would be reported all round the world. This is the world of Max Mosley.

And yet he is not merely a figure of curiosity, a sort of litmus test of our own curiosity into the sexual habits of the great and good. Mosley is also, still, the president of the FIA, which means he oversees motorsport in general, and Formula One in particular. In a sport of huge budgets and global reach, he is a very significant player, one who has remained at the top of his tree despite various entreaties thrown at him to step down. The response has always been the same – that he would know the time to go, and that he would not allow himself to be shoved aside.

It is a streak of confident defiance that runs through Mosley like a seam in a rock. I guess that over the past decade I've sat down half a dozen times with him to conduct interviews in which I rather hoped to catch him out. That's the game when a journalist chats to a big sport administrator – we try to get them to say things they shouldn't, to give away a few secrets, perhaps to release an indiscretion or two.

And with Mosley, you often get very interesting comments, unpredictable analysis, a clutch of barbs. But you also get the impression that he knows exactly what he's doing. He trained as a barrister, and is still the most eloquent and mentally dexterous person I've come across in sport.

And now he sits across from me, daring me to try to outwit him again. Except this time, there are no games to play, no obscure areas in which to try to lure him. Everyone wants to know the same things, I guess, so I ask them. What happened that Sunday morning when the News of the World story came out, and your life turned upside down?

"I found out about 10 o'clock that morning. I got a phone call from our press man Richard Woods, asking me if I had seen the paper, and I said no. So I went and got a copy, and I thought it was quite extraordinary. It was shocking but it was also immediately apparent to me that it was completely illegal.

"I was at my wife's house and my son was there as well. I showed them the paper, and my wife's first reaction was that she thought it was a joke, that it was a front page that I'd made as a practical joke. It's the sort of thing I might do. But after that, for all of us, it was a question of 'what are we going to do about it?'"

What he did, of course, was to instigate legal proceedings against the paper. And yet I was curious about his apparent lack of remorse. Did he not think that he was in some way culpable for what had happened? Apparently not.

First of all, Mosley never expected this would happen. He had always chosen his friends very carefully, he said, and had been discreet in what he did. Furthermore, "I thought it would be illegal for them to publish, and I assumed the papers would obey the law". But what about the act of lying to his wife for 50 years – 50 years! – about what was going on. A shrug. "It is something that is between you and your wife, not something that should be discussed in public. It is something you shouldn't do, but human nature being as it is, it is not exactly uncommon."

His point, of course, is this – that if someone's personal life is conducted in a legal fashion, then why should it concern anybody else. Later on, he tells me the effect on his wife and two children has been "catastrophic". They have not, he says, come to terms with the newspaper revelations, nor with the impact of the court case.

He, on the other hand, seems to be hobbled by no such doubts. On the contrary, his quest for legal redress marches on. Mosley is pursuing action through the European Court of Human Rights in Strasbourg to try to impose a change on British law. If it comes into effect, newspapers would be obliged to offer a right of reply to people before stories are published, a privilege that was never afforded to Mosley.

In effect, what he wants is for the victims of sensational stories to be given the opportunity to take out an injunction, preventing publication. In Mosley's particular case, the facts are there – the editor of the News of the World made it quite clear in court that it was the very fear of an injunction being issued that stopped him contacting Mosley before the paper went to press.

So is this vengeance, I wonder? After all, I don't remember this cause ever being mentioned by Mosley before his own embarrassing run-in with a red-top juggernaut.

"Well, that's true. But then again people often only get involved in a road safety campaign when they've had the misfortune of seeing a family member or a loved one injured in a crash, so one is certainly influenced by personal experience. But the thing that gets to me is that every weekend, tabloid press ruins someone's life. And once it's done, it cannot be undone. It should be a judge who decides if it's worthwhile, not a tabloid editor. If the paper proves their case, they can publish their story. But if they don't, then the victim does not end up suffering irreparable damage."

This, for Mosley, is a crusade, and it is one he is taking up with gumption. He will stand down from motorsport next year, citing weariness rather than any embarrassment over his actions. But you guess that while he may be tired of the politics of motor racing, his enthusiasm for this battle with the media is not about to wane.

But there is that year to go, and it may be an absorbing one. Not so much because of the racing – although he admits Lewis Hamilton has brought "a whole new audience" to Formula One – but because he believes the very fabric of the sport is under threat.

When I asked him about the effects of the global credit crunch on Formula One, Mosley's response was candid, and worrying. "Our problems are not just because of the credit crunch – they've been around for a while now. It's becoming apparent that Formula One is unsustainable. A team at the back of the grid can only raise about £30m, but to compete they need two or three times that amount, and you just can't run a business like that.

"We have got two gaps on the grid at the moment for teams, and we may end up with two or three more. And if we get a grid with, say, only 14 cars on it then it would cease to be a credible sport. The costs have got to come down. The days when manufacturers would plough 200 or 300 million euros in per season have gone. I think we can survive through 2009, but if we don't get this done by 2010, we'll be in serious difficulty."

Now, there is a bit of posturing in here, a bit of Mosley showing himself to be the strong leader, but there's also plenty of sense. The world's economy is falling apart; the globe's most cash-laden sport can hardly remain aloof from all that. And the spectre of a race involving barely a dozen cars is dreadful.

He spoke fluently and honestly, and he was engaging. Not once did he avoid a question, and not once did he look embarrassed either for himself or me. At 68, he still has a blaze in his eyes, a streak of utter independence. "Have you changed your lifestyle since the newspaper exposé?" I asked. "Oh no, not at all," he replied, surprised that I would countenance such a thought.

He is defiant and he tells me he's happy. His family may be struggling with the hurricane that's hit them, but Max Mosley seems serenely and remarkably energised.