Dominic Lawson: So what turned David Irving into an apologist for racism and genocide?

"All the scum of humanity stand outside. The homosexuals, the gypsies, the lesbians, the Jews, the criminals, the Communists..." If a team of undergraduates were asked on University Challenge to identify the author of that remark, I suspect a bright young history student would immediately press the buzzer and tell Jeremy Paxman : "Adolf Hitler." In fact I am quoting the words of a man who himself is widely described as an historian. They come from a video entitled David Irving : Ich komme wieder.

For the record, what David Irving was describing was the crowd who demonstrated outside his Belgravia apartment when he was contracted by The Sunday Times to assist the newspaper with their serialisation of the Goebbels diaries. Given that Irving had some years earlier been one of the "experts" who said that that newspaper's Hitler diaries were the genuine article, it was perhaps surprising that The Sunday Times should have employed him.

But it was not until Irving's unsuccessful attempt in 2000 to sue the writer Deborah Lipstadt for calling him an anti-Semite and Holocaust denier, that he was comprehensively exposed as a man whose exhaustive research into the events of the Second World War were motivated not by a disinterested search for the historical truth, but by a burning desire to justify Hitler and his philosophy.

It is well worth reading Lord Justice Gray's 333-page judgement in Irving vs Lipstadt for a full flavour of Irving's "historical method", but here's just one example from the judgement of how Irving attempts to persuade the readers of Hitler's War that the Führer did not plan or desire the slaughter of the Jewish populations of Europe: In Hitler's Table Talk of 25 January 1942, the Nazi leader says to his dining companions " The Jew has to get out of Europe; if he collapses in the course of it, I can't help there. I can see only one thing: absolute extermination if they don't go of their own accord."

Irving quotes the first sentence - but not the second one. It's almost disappointing, really: this is the sort of childish trick that would get an undergraduate history essay gamma beta - at best.

The court in Viennna last week was not , of course, passing judgement on Irving the historian. Irving was on trial for what he said in speeches in 1989 to his Austrian fan club. The Times reported from one of the gatherings that Irving told his admirers the testimonies of so-called Holocaust survivors were worthless since they were "psychiatric cases" and that of the six million European Jews who disappeared, 74,000 died of natural causes in work camps and the rest were hidden in reception camps; from there they were "transferred to Palestine" where they took on assumed identities.

A number of commentators, including Deborah Lipstadt, have questioned the wisdom of sentencing Irving to three years' imprisonment for something that he said 17 years ago. I certainly don't think that anyone should be imprisoned in this country for something he said 17 years ago - no matter how offensive. But Irving knew very well that there was an arrest warrant still out for him in Austria. Indeed, his wife and friends warned him not to go. He replied, characteristically "I am a soldier. I march towards the sound of gunfire." Well, those who do occasionally get hit by a bullet.

Rightly or wrongly, the laws of every country limit freedom of speech in ways which reflects that country's history. In Britain, for example - where there is a substantial black and Asian population - there are laws which can be used to jail people for expressing views which might incite racial hatred. They were recently invoked to prosecute Nick Griffin, the leader of the British National Party.

The politicians and courts of Austria have slightly different concerns. Although there are only about 7,000 Jews left in the country, its experiences in the Second World War still lie heavily on the national consciousness. The Allies treated the defeated Austria as a victim of Nazism, rather than a collaborating nation, despite the enthusiasm displayed by its people for the extirpation of the Jews. So there was no de-Nazification of the sort imposed by the Allies in post-war Germany. The Austrians had to do it for themselves.

Hence in 1947 they brought in the law against neo-Nazi activity, which prohibits any form of neo-Nazism or anti-Semitism, including - this may interest you, Mr Blair - the "glorification of National Socialist Ideology". This is the law which has snared David Irving. Despite Irving's claim to the Vienna court that he is no longer a Holocaust denier, his website - which of course can be accessed in Austria - shows that he is still up to his sly old tricks.

This is from an entry in May 2005: "We have no idea who the mountains of shoes at the Auschwitz tourist centre come from, forensically speaking. We do know that footwear was routinely removed from the bodies of German air raid victims, including thirty tons of clothing from those killed in the Dresden air raids alone and turned over to recycling agencies."

The bombing of Dresden is Irving's standard counter charge to those who accuse the Nazis of war crimes. And there is an appetite for this sort of thing in what used to be called "Greater Germany". In February 2000, I flew out to Klagenfurt to conduct the only British newspaper interview with Jörg Haider, the Freedom Party leader who had just had astounding success in the Austrian elections. In the past, Haider had expressed support for the employment policies of the Third Reich, and had claimed that Winston Churchill was a war criminal. When I asked him if he still had that opinion about Churchill, he did not demur.

Later that month, Haider's party became part of the Austrian governing coalition: the European Union responded by barring all Austrian politicians from its governing councils. Distasteful and creepy as I found Haider - and he threatened to sue me for the article I wrote about him - I thought the EU's reaction was undemocratic and grossly improper. Nevertheless it shocked the Austrian political class to its core - which may be one reason why the law against neo-Nazi activity has not been revoked.

One mystery remains. Why did David Irving, an intelligent man in many ways, become such a Germanophile anti-Semite in the first place? He comes from a service family - his father fought against Germany in both world wars and his elder brother reached the rank of Wing Commander in the RAF. In 1956 young David Irving presented himself at the RAF recruiting office in Holborn. But despite getting, he claims, "the highest result in their IQ test that they had ever recorded", a bitterly disappointed Irving was rejected as "medically unfit for military service".

It was, of course, the RAF which bombed Dresden. Perhaps Irving's whole career is a form of revenge.

d.lawson@independent.co.uk