How an historian took on an infamous Holocaust denier

History buffs packed out a lecture theatre at University of Otago's Wellington Campus on Sunday to hear a famous historian recount how he overcame an infamous Holocaust denier.

The courtroom clash of Sir Richard Evans and David Irving has even been made into a film, Denial.

Sir Richard's work has made him one of the world's most famous historians, a status backed up by his depiction in Denial. It tells the story of a landmark libel trial 17 years ago brought by prominent Holocaust denier Irving, known for his racist and anti-Semitic views.

Irving sued an author for claiming he falsified history.

Played by actor John Sessions in the film, Sir Richard was called as a witness. His task was to prove the Holocaust really happened.

"In the movie I'm on for about three minutes. Actually I was about 28 hours in the witness box," he told Newshub.

Sir Richard is on a lecture tour of New Zealand, discussing the trial and his experience of being cross-examined by Irving - a man who in 2004 was denied entry into the country.

"I got the measure of him after the first hour or two, and what I came to realise is that you can't trust anything he says."

During the trial old plans were found of the Auschwitz concentration camp, which disproved Irving's claim there were no holes built in the ceilings of gas chambers to drop cyanide - a popular theory among Holocaust deniers.

"One shouldn't exaggerate its importance," Sir Richard said.

"It's distasteful; it's unpleasant and it's upsetting... and I think we have to do everything we can to combat it."

Irving lost the case and was ordered to pay £2 million in legal fees, while the verdict made Sir Richard a target himself.

"I had a sack full of abusive hate mail, which I've preserved for my biographer."

But Sir Richard said the abuse was worth it, as the verdict again underlined the evil of Holocaust denial.