Leading article: Laugh where we must. And we must at this judgment

Sir Gavin Lightman is no fool. He wrote a learned tome on property law and once prospected Libyan gold mines for the National Union of Mineworkers. On the rights of gay servicemen, he last year returned a liberal, Euro- friendly verdict. No bewigged fop, he is media-savvy, having judged case involving newspapers and pop stars; he could doubtless name the Spice Girls, they too having come before his bench. But for all his distinction, Mr Justice Lightman yesterday made a bad error of judgment which, if it stands, will damage the public life of this country.

His conclusion in the Alan Clark spoof diaries case not only betrayed a lack of a sense of humour and insulted you - the readers of this and every other newspaper - by implying you are stupid. Seemingly unaware, he also set the legal cat among the pigeons on privacy and the ability of famous people to copyright their images. Worst of all, he sought to diminish the public space within which we conduct our collective and political life and so threatened our capacity for honest self-government.

The point about Alan Clark is not that he is lecherous, cruel, publicity- hungry or a political failure whose tendentious readings of the history of the Conservative Party are not only misleading but an awful basis for the necessary work of rebuilding the principal party of the right. The point is that he is, beyond any dispute, a public man. He thrusts himself into the limelight, wherever that can be found. He is an elected representative of the people.

Let's be clear. Such a man deserves the full protection of the law. If he is assaulted in the street, say by the husband of one of his conquests, we would expect a constable to come to his aid. But if the law says this man cannot be drawn in cartoons, reported on, editorialised about and satirised, it is a self-evident ass. Given Clark's extravagance of language and behaviour, he is, admittedly, hard to parody - this is after all a man who calls his dogs after Adolf Hitler's girlfriends. Yet Mr Clark, his face straight, told the court he is a serious person with a literary reputation who has been bruised by a parody which people might believe to contain the truth. Had the Evening Standard articles not been so highly coloured and extreme they would not have been credible as Mr Clark's own work. This is tosh. Alan Clark inhabits a realm that lies far beyond the Copyright, Designs and Patents Act.

But no, said the learned Mr Lightman. Aping a style for the purpose of mockery constitutes breach of copyright. If true, that obliterates a whole literature of witty parody. Moreover, it seems, newspaper readers cannot understand, let alone take a joke, and Mr Clark's solicitors found a dozen humourless Londoners (including - surprise, surprise a brace of solicitors) to prove their point. But we assert that they can. Without the spice of humour, newspapers would be dull dogs indeed. Without the capacity to take off, to cock a snook, sometimes to humiliate the grandees of public life, an essential element of journalistic purpose would go.

Mr Justice Lightman, however, sees no distinction between the self-interest of a public man, engaged in controversy and television shows, and the protection of private property. We do. The difference goes to the heart of the stuttering debate about privacy and the media. There is a case, now becoming urgent, for a parallel review of the libel law and the protection afforded by the law to people written about in newspapers and reported on in the electronic media. Some say that we can relax and let the clauses of the European Convention on Human Rights, now being absorbed into domestic law, take their course. No. If Mr Justice Lightman is representative of the likely attitudes of the bench to critical divisions of public and private interest, this approach is doomed. The way forward looks increasingly like legislation that cements the rights of private individuals to privacy and their freedom from media abuse within a context that recognises the right - duty - of newspapers to speak for the public on public matters. What is "public" is not hard to define. It embraces politicians, the prominent, those in leading positions in business and culture, controversialists.

Alan Clark is not a private man. He is preparing a second volume of diaries. Unless his publishers are idiots (which Weidenfeld's are not) they will expect lashings of sex and much dirt on John Major and his ministers. Perhaps as a result the gaiety of the nation will be augmented and Alan Clark will become richer. What he will also become is even more notorious, even more a legitimate subject for criticism, conversation and, yes, scathing parody. Let us hope the Standard appeals, and defeats this daft judgment. Meanwhile, we will do everything we can to continue lampooning Mr Clark, since that is what he so obviously invites us to do.