Max Mosley's case is the frontline in a legal battle for freedom of expression

The case that could define the future freedom of the British press contains some of the key ingredients of a Whitehall farce: a seemingly respectable middle-aged man caught with his pants down, drinking tea and chattering away to scantily clad women in the language of the sitcom 'Allo 'Allo!: "Zey need more of ze punishment, I zink."

Yet, the legal action for breach of privacy being brought by Max Rufus Mosley, president of the Fédération Internationale de l'Automobile, against the News of the World is no matter for tittering – despite the fact that 1.4 million people have accessed the paper's website to do just that at video footage of Mosley's encounter with five prostitutes.

The hearing, which begins today in the High Court before Mr Justice Eady, is deeply serious. To Mosley, the breach of his privacy and the paper's description of his S&M activity as a "Nazi-style orgy" are so malicious that he is entitled to exemplary damages. For News of the World, the case is not simply the latest in its long tradition of vice-related exposés, it is a revelation of the depraved and violent behaviour of an elected official with global influence.

And there is little laughter in the ranks of the British media, where the realisation of the potential implications of this case is beginning to take hold. "This is a landmark case and journalism has everything to fear – and not just tabloid journalism," says Ian Reeves, director of teaching at the University of Kent's centre for journalism. "If Mosley was to be successful in this case, then it does fundamentally change the landscape."

The motor racing chief has brought his action under article eight of the European Convention on Human Rights, which guarantees his right to privacy. It is the same piece of legislation that has been used by other celebrities, including Princess Caroline of Monaco and Naomi Campbell, against perceived media intrusion. News organisations such as News International, which owns News of the World, have often sought to defend themselves by citing article 10 of the convention, which protects freedom of expression. Yet, so far, the media have met with little success.

"What happens in these cases is that the court seems to favour privacy over the public's right to know," says Bob Satchwell, chairman of the Society of Editors. "The courts seem to have sympathy for celebrities rather than the interests of the media. You have the suspicion that there is distaste for the kind of publications involved. The law seems to be being made by these exceptional cases involving celebrities, and quite often involving papers where you feel the judge is looking down their nose. It would be absolutely wrong if a privacy law was brought in by the back door simply because the story concerned a celebrity and originated from a paper that the judge disliked."

According to Satchwell, the successive defeats of the media in privacy cases is building up a body of case law that could weigh heavily in future hearings – ones that are perhaps more serious than a tabloid sex exposé. "If these cases are decided in a way that goes against the media, they will be used, at some stage in the future, in a fundamentally more important case – say, for instance, something involving a senior politician and a very serious investigation by what some judges might consider to be a more respectable broadcaster or newspaper. That's the worry."

Certainly that is a view inside Wapping, where Tom Crone, legal manager of News International, says: "I think this is quite an important case in just how far article eight should be allowed to go in suppressing reports on extreme activities."

Within legal circles, the chances of the newspaper carrying the day are seen as limited. Keith Mathieson, a media specialist at City law firm Reynolds Porter Chamberlain, says: "A lot of the article eight cases are being decided by the same judge, David Eady. So far, he has shown a fairly strong inclination to protect the individual's privacy rights, and a disinclination to pay too much attention to what the media wants to publish."

Mr Justice Eady ruled in 2005 that the privacy of the Canadian folk singer Loreena McKennitt (left) had been infringed by a former friend, Niema Ash, who had written a book about her. In another case, also involving article eight, the same judge granted an order protecting a prominent figure in the sports world from being identified in a newspaper by the husband of the woman with whom the sporting figure was having an affair. Then last year, Mr Justice Eady presided in the case brought against The Mail on Sunday by the former chairman of BP, Lord Browne, granting an injunction that prevented the full story from being published.

Mathieson is convinced that News International will find the judge unsympathetic. "I would have thought the chances are that Mosley will win and Eady will find there's no overwhelming public interest to justify this invasion into Mosley's privacy. It's unfortunate, because it builds up a body of law which makes it look as if privacy rights will always trump publications' freedom of expression rights," he says. "Unfortunately, not too many strong public-interest cases have come before the courts so far. The cases have tended to be tittle-tattle, rather trivial stuff, not important issues."

Nonetheless, he remains confident that judges will, in future, distinguish between less and more serious allegations – and that in the latter cases, the right to freedom of expression will weigh heavier. "We are still at a pretty early stage of developing a privacy law, as the cases before the courts are quite specific. While the likes of the News of the World don't like these cases, because they stop them doing this kind of exposé, I'm afraid that's the tension between the tabloid press and the courts."

News of the World would disagree with the suggestion that the Mosley story amounts to little more than gossip. It will seek to persuade the judge that the Formula 1 chief's behaviour was brutal and his sexual activities depraved. It will argue that Mosley's German speech (and English spoken with a bizarre German accent), and the wearing of uniforms that it maintains were German, all justify its claim that this was a role-play exercise inspired by German military history, 1939-45.

Mosley, the son of Sir Oswald Mosley, who founded the British Union of Fascists, has described the allegation that his actions were a "Nazi orgy" as a "deliberate, cold-blooded, calculated lie", though he did not deny taking part in the orgy. He is represented by the solicitors Steeles Law and has promised to donate any damages to the FIA Foundation, which promotes motor-sport safety and the protection of the environment.

The hearing is expected to last for two weeks.