If David Irving had not decided to sue an obscure American academic and Penguin Books for allegedly defaming him, his reputation as a historian might, at least to the uninformed, have survived a little longer.

He did not have the academic credentials now normally required of professional historians and he was not an academic, but he had over the years won the grudging respect of academics for the stamina and assiduity with which he worked in the archives to produce material not seen before.

Writers as eminent as Sir Winston Churchill's biographer, Sir Martin Gilbert, military historian Sir Michael Howard, and Hugh Trevor- Roper, author of the brilliant classic work on the last days of Adolf Hitler, had all been prepared to praise him for the energy with which he conducted his research.

Since the 1960s, Irving has been prolific. He has concentrated on the central figures or events of World War 2, producing large volumes on the bombing of Dresden, and on Goering, Goebbels, Churchill, Rommel and Hitler.

For all his energy, however, there have been doubts from the beginning about the conclusions he drew from his research.

In one of his earliest books, about a British convoy taking supplies to Murmansk in northern Russia during World War 2, he accused a British officer of cowardice leading to the destruction of the convoy.

A court found that this was a gross libel, and awarded damages against him of 40,000, a huge sum at the time.

In the late 1970s, he published Hitler's War, a "revisionist" work which set out to distance Hitler from responsibility for the Jewish Holocaust.

Reviewing it for the London Sunday Times, Hugh Trevor-Roper conceded that the work had some merit, but he crushingly concluded that Irving was not to be trusted.

"We can never quite be sure, and when he is most original, we are least likely to be sure."

He found that Irving wrote with a "consistent bias".