Irving was arrested in November during a visit to Austria to address a right-wing student group. He was charged with denying the Holocaust, a crime in Austria, in two speeches he had given in that country in 1989. The indictment quotes his description of the Nazi gas chambers as a “fairytale”, and his claim that Hitler knew nothing about the slaughter of Jews: “There were no extermination camps in the Third Reich,” he is quoted as saying. If convicted, he faces up to ten years in prison.

Irving’s views are repulsive and wrong. He is a deeply offensive crank, and a litigious one, who has tried to use the libel laws to silence his critics. Five years ago, he sued the American historian, Deborah Lipstadt, after she described him as a Holocaust denier, and lost. In a withering 333-page judgment, Mr Justice Charles Gray described him as an anti-Semite, a racist and a neo-Nazi sympathiser who had “persistently and deliberately misrepresented and manipulated historical evidence”.

Irving’s opinions are indefensible; his right to hold them, however, must be defended. For reasons of both principle and expediency, he should go free. Freedom of speech includes the right to be hopelessly, demonstrably and repeatedly wrong. It is not to be applied selectively, depending on the nature of the speech in question, but universally and consistently. The UN Declaration of Human Rights is unequivocal: “Everyone has the right to freedom of opinion and expression.”

To defend free speech when we happen to share the speaker’s opinion is an easy task. Take Orhan Pamuk, the Turkish writer who is facing trial for saying, in defiance of the official Turkish view of history, that his compatriots carried out the genocide of Armenians during the First World War. Many writers (including this one) have defended his right to do so. Far harder, but just as essential, is the defence of speech that we find morally disgusting and intellectually bankrupt. When a conference in Turkey on the Armenian question was cancelled under state pressure, the liberal West was outraged; when Iran recently announced a conference to question the authenticity of the Holocaust, the West was, once again, outraged. But in the case of both Irving and Pamuk, the issue should be settled in the court of public discussion, not the law courts; so long as speech does not directly incite racial hatred, it must remain free.

In 1947, when the Austrian law against minimising Third Reich atrocities was promulgated the fear of resurgent Nazism was real. But should it still apply today, when Holocaust denial has been so thoroughly exposed for the malicious nonsense it is? There should never be an official version of history that cannot be questioned. History will often fall into the wrong hands, where it may be twisted to suit a preconceived prejudice, but that is a lesser evil than undermining freedom of speech.

Lipstadt herself, after a career spent destroying the arguments of Nazi apologists, believes that Holocaust denial should not be a crime, and that keeping Irving in Josefstadt prison is counter-productive.

The trial of Irving, due to start next month, risks saving him from the intellectual oblivion he and his views so richly deserve. Before the Austrian police arrested him, he was a fringe academic addressing a group of loopy far-right radicals wearing silly hats in a basement in Vienna. Now there is a real danger that he will become a martyr for the extreme Right. After his humiliation in the High Court, Irving all but vanished from the world’s attention; his arrest has generated headlines around the world, and by putting his views on trial, they will gain a credibility that they simply do not merit.

For Austria, beset by the rise of the far Right in the unpleasant shape of Jörg Haider, Irving has appeared at a politically opportune moment. Sticking the “revisionist” in prison for something that he said 16 years ago, based on a law nearly 60 years old, is a neat way for Austria to demonstrate its liberal bona fides. Of the nine countries with laws banning Holocaust denial, Austria is the strictest. Yet the country has too often shied away from admitting its Nazi past.

The Simon Wiesenthal Centre estimates that some 40 Nazi suspects are still living in Austria, and accuses Austria of a lamentable record in apprehending war criminals.

Irving is in prison for writing about the Holocaust, in a country where people who took part in the Holocaust are still at liberty. Irving would be able to argue that the people who operated the gas chambers should be prosecuted before people who make speeches about them, except that he is on record as saying that the gas chambers never existed. Ironies don’t come much more savoury than that.

Irving and his like have caused deep anguish to survivors of the genocide and their families. But the vast majority of people know that the Holocaust happened, that Hitler caused it, and that those who argue otherwise are not interested in the truth. We should not need laws to enforce that knowledge.

The way to arrest the pernicious myth of Holocaust denial is not through the police, but with rigorous analysis, followed by disdain. When the deniers assemble in Tehran for their “scientific” conference on the Holocaust, their claims should be listened to attentively, demolished scientifically, and then laughed off the stage and forgotten. They should not be arrested.

Let Irving go. In Lipstadt’s words, “let him fade from everyone’s radar screens”. He is a blip, a tiny spot beyond the outer edges of rational debate that has attracted unwarranted attention. He has a right to be wrong; and once he is at liberty, we can all exercise our own inalienable right to ignore him.

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