The Regional High Court in Vienna upheld an appeal by Irving yesterday, converting into probation the three-year sentence handed down last February. Irving, 68, was arrested in November last year during a visit to Austria on a warrant dating back to 1989, when he held two lectures in Austria denying the existence of death camps and the organised mass murder of Jews during Nazi rule. He was held under a 1992 law that makes denial of the Holocaust a crime.

Irving said yesterday that he was fit and well. “I have been in solitary confinement for 400 days and you can imagine how awful that is,” he said.

He now plans to hold a news conference tomorrow evening, calling for an academic boycott of German and Austrian historians until their governments stopped putting historians in prison.

Bente Hogh, his partner of 15 years, told The Times last night that he had been transferred to an open prison and would be deported this morning. “He rang me from outside the courtroom saying he had won,” she said. “He was due to fly back on Wednesday afternoon, but there were problems with the weather at Vienna airport and he was taken back to prison.”

The panel of three judges took no more than 15 minutes to make their decision. Justice Ernest Maurer announced the ruling in front of about 20 visitors in the small court room, which included supporters of Irving, some of whom had reportedly travelled from neighbouring countries.

State prosecutors had requested an increase of the sentence, claiming that it was insufficient because Irving appeared unrepentant and served as an idol for far-right movements in Austria and abroad.

Marie-Luise Nittel, the senior public prosecutor, said that Irving’s words should in no way be underestimated. She told the court that he was “like an idol, whose words provide the basis for the right-wing scene”.

The court heard abstracts of the original charges, in which Irving was quoted as saying that Hitler extended a protective hand to the Jews, that there were no death camps during the Second World War and that Holocaust survivors claiming the opposite should be subject to psychiatric examination. “Is it not time to stop this gas chamber fairy tale?” Irving was quoted as saying.

Justice Maurer said that the court had taken into consideration that Irving had already served more than 13 months in prison, as well as that he had apologised and taken back his claims and that he was an elderly man separated from his London family.

Irving was banned from talking to the press and left the court room immediately after the ruling. He had put on weight since his last hearing in February and during the trial held a copy of Agatha Christie’s Passenger to Frankfurt.

He appeared in good humour and joked with the guards, who were in charge of preventing him from speaking to the press. He told one of the guards that he had suffered bad luck during the first trial because “seven members of the jury were women: very bad”.

His lawyer, Herbert Schaller, admitted to The Times later that he would not allow Irving to speak to the press while in Austria, fearing that he might end up in trouble with the law again.

He said: “I advised Mr Irving to leave the country as soon as possible. I believe he will do exactly that without looking back. I don’t believe he will want to return to our dear fatherland ever again.”

Gerhard Jarosch, spokesman for the Vienna public prosecutor’s office, said that the authorities were considering new charges against Irving for a series of interviews he gave while in prison in which he partially restated the controversial views for which he was jailed. He said: “There is an open case against him on account of the prison interviews but it will surely take weeks before we reach a decision on it. In the meantime, Mr Irving is a free man and can travel back to Austria as he pleases.”