Since then, Gitta Sereny, Irving's indefatigable chief critic and, like him, one of the world's best-versed students of Third Reich archives, has repeatedly challenged various versions of events put forward by Irving. She is one of the few people to have trawled through the same documents as Irving and interviewed many of Irving's witnesses. Sereny has also established herself as a major biographer of the Nazi period, publishing acclaimed studies of Franz Stangl, commandant of the Treblinka extermination camp, and, last year, of Albert Speer, Hitler's munitions minister and favourite.
This week, Irving's patience finally snapped; it was announced that he is suing Sereny. His legal objections spring from her latest broadside against Irving's new book, which argues that Joseph Goebbels, the Fuhrer's propaganda chief, was in fact the originator of the Final Solution, goading on Hitler, rather than being led by him ....
David Irving does not like Gitta Sereny. He has not liked her since 1977, when she went through his book Hitler's War with forensic care and pronounced him wrong about Hitler's alleged lengthy ignorance of the Nazi's genocidal policies. "She was a shrivelled little prune then. And she is a shrivelled little prune now," he said this week, shortly after it emerged he has served a libel writ on her.
"I am very anxious," he said "to clear my name of the allegations that I have distorted anything. When allegations are made against a serious historian - I have published 30 books in the past - they cannot go unchallenged. It may be that she will turn up at the High Court with a few examples of how I distorted. Then I will have mis judged myself. I very much doubt it."
Sereny is, he believes, a critic who has gone too far in attacking his belief that Hitler may have known little of what was going on. She has also challenged Irving's questioning of the very existence of Nazi gas chambers.
Ever since 1977, he says, "she found me in her corner, so to speak, using the same sources, jostling over the same trough. I often get bigger notices than her. I end up getting better sources than she does. Ironically, I asked one bookshop to take my biography of Goebbels. I was told the shop wouldn't be taking it because Gitta Sereny's book on Albert Speer did so badly, which surprised me because I thought it had done well. So it was ironic that I was blocked by her failure. In a tiny way, she has proved my nemesis.
"A feud like this doesn't usually last 20 years. I bear her no ill will whatsoever. I'm quite happy to co-exist with her as long as she sticks to fair means. For a number of years I have shown patience, but I've stopped showing the other cheek. I now realise that I'm under worldwide attack."
He is furious that earlier this year she wrote in an article (now subject to his libel writ) that she was pleased he had been banned from using archives. The ban, in Germany, has left him bereft. He has not been back there since it was imposed. "As a result, I'm divorced from my publishers, my sources, my archives, my friends."
He does not think there would much point in a one-to-one debate with his rival and critic, as suggested by the Independent. "I don't think it would be positive. I think her mind is now totally ossified. We would be speaking on different planets because I don't think we speak the same language. I would probably be offensive to her and she to me."
And he remains confident that Hitler has had a bad press. "There was," he says, never a "document linking Hitler to what happened to the Jews on the scale of what is now called the Holocaust. There has to be a logical reason for it."
However, he concedes that he might be wrong about Hitler's culpability. "I'm prepared to accept that it may have been on the threshold of his knowledge. It may be what I call the Richard Nixon complex. He may have said: 'Look, fellas, go out there and do it. You know what I want done. Just keep me out of it'.
"I have no axes to grind. So I don't mind if one day I am proven wrong. I think you will then see me adopt a little bashful smile and utter some such phrase as I gave them a good run for their money for over 20 years."
But wouldn't a "bashful smile" be a little inadequate as way of apology to the survivors of the Holocaust, and the relatives of the victims? "It's not my fault," he replied. "It's not my fault if their champions have been unable to prove me wrong for 20 years. If the best Sereny can say is 'Thank heaven he is not allowed to use the archives', then she is not much of a champion either."
Gitta Sereny read Mein Kampf at 11, heard Hitler address the Viennese at 15 and briefly attended the Nuremberg trials in 1945. A Hungarian, born in Vienna into a landowning family, she is not Jewish. A diminutive figure, she is still, at 72, admired for her tireless investigative approach not only into Nazi history but also into murders committed by children. She has written a classic study of Mary Bell, convicted of two murders, and of the two boys jailed for killing two-year-old James Bulger.
When she first encountered David Irving in 1977, she says she was impressed. "I was intrigued by his book Hitler's War. My first thought was that it was very good. I thought his idea - which turned out to be wrong, namely that Hitler did not know about the Holocaust - was just possible."
But close examination of his work - she was commissioned to spend six weeks re-examining the papers, archives and witnesses used as evidence for Hitler's War - convinced her that Irving's thesis was mistaken. "Twenty years ago, he was dangerous," she says. "He is attractive. He does wonderful research and has a talent for writing. People respect it. The tragedy is that he has misused these talents. Irving could have made a tremendous addition to knowledge. He brought all this on himself. No one did it to him.
"He is obsessed with a number of things, his feelings for Hitler and his own feelings about the Jews. He has great sympathy with Hitler and that makes him dangerous. I am the red cloth for him because I am as familiar as he is with the areas he writes about. In 1977 I analysed his book and I believe that my conclusions were very disturbing for him. But if you think of all the things that I have written, he is a very small part of my life. He cannot see this: he believes that the little I have done has caused him damage.
"Why bother, you may ask, to write at all about this disaffected man, who so sadly abuses his undoubted gifts? The reason is his books .... It is essential that the public is alerted to his treatment of history. With a well-presented book, how many readers, lacking specialised knowledge, can be expected to detect errors and omissions? I made him most angry in 1977 when I accused him of mistranslating something. Anyone who speaks German as a foreigner can make mistakes. He speaks very good German, but obviously my knowledge is deeper.
"We use the same sources, particularly through my work with and on Speer. I know many of the same people as he does who were of Hitler's circle. That is scary for him. He says we jostle at the same trough. The difference is that he loves the trough and I don't. He admires Hitler enormously. I gained a lot of understanding of Hitler, particularly through my work on Speer. Everything I have come to understand about Hitler horrifies me - even his very human sides. You would think once you discovered the human aspects, your attitude would change. But it can't change for me. I know too much of the other side."
It is intriguing that Irving's wrath is focused not primarily on the academic debate with Sereny but on her support for restrictions on his use of archive material. It is as if he is panicked by the prospect of being prevented from doing what he does best and probably loves best - examining historical documents.
"Researching history will, thank heaven, become increasingly difficult for him," Sereny said in the article which prompted the writ. Asked about this remark, she now says: "Using archives is a privilege. It is a right, in that they are there for serious researchers to use. But you can't abuse it.
"He is silly to challenge me, because I will, of course, prove what I said. I think it will cost him a fortune. It will be a pity for him. There is, I think, despair in all of this."
It looks, however, as though the feud, which has lasted 20 years already, will carry on regardless of how this latest spat is settled. And whatever the outcome, the careers of Irving and Sereny seem destined to remain interlocked. Irving's biography of Goebbels is currently being advertised by Irving with a racy flier. "One brilliant propagandist ... writing about another," is the comment by the quoted reviewer.
And who might that be? None other than Gitta Sereny.