It was banned nearly 30 years ago for its graphic scenes of incest and real sex.

But the controversial Roman epic Caligula is set to be sold on the High Street after the British Board of Film Classification finally gave it the green light.

The original 1979 movie was scripted by the writer and historian Gore Vidal and featured a host of stars including Helen Mirren, Peter O'Toole and Sir John Gielgud.

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Helen Mirren in a scene from Caligula. An uncut version of the 1970s film is set to make its way on to the High Street after censorship was lifted

It was meant to be an historical drama, detailing the excesses of the third Roman emperor Caligula, whose rule from 37-41AD was dominated by violence and debauchery.

But Bob Guccione, founder of pornographic magazine Penthouse, who produced and financed the film, felt it did not contain enough sex.

He secretly filmed graphic real sex scenes performed by porn stars and inserted them into the final edit.

Malcolm McDowell played Caligula in the film about the third Roman emperor

Although it was subsequently released in the U.S., officials here banned the film because of its gratuitous content. Vidal later asked for his name to be removed from the movie's credits, while actor Malcolm McDowell, who played Caligula, said: 'I'm proud of the work I did, there's no question about that.

'But there's all the raunchy stuff, the blatant, modern-day porn Bob introduced into the film. That to me was an absolutely outrageous betrayal and quite unprecedented.'

Although the film is available in this country on DVD, it is a heavily sanitised version and almost an hour shorter than the uncut Imperia edition.

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Scenes taken from the British version of the 1979 film. But director Bob Guccione, who produced the film, filmed and added graphic sex scenes with porn actors which was subsequently released in the US, but banned in the UK

Sue Clark, spokesman for the BBFC, defended its decision to allow the uncut edition in the UK, saying that certificate 18 guidelines state 'adults should be free to choose their own entertainment within the law'.

She added that, despite the pornographic sequences, the film did not fall into the category of sex work, because its aim was not to arouse viewers. It is not the first time the BBFC has allowed movies featuring real-life sex to be released.

In 2004, Michael Winterbottom's 9 Songs stunned critics with its graphic scenes.
The BBFC has also come under fire in recent months by giving certificates to films featuring graphic scenes of sex and violence.

Last month, it was heavily criticised for awarding Batman: The Dark Knight a 12A rating, despite concerns about the level of violence.

Last year, Tory MP Julian Brazier attacked its decision to pass for general release the film SS Experiment Camp, which was banned 20 years ago by the Director of Public Prosecutions.

In one scene, prisoners are shown being boiled alive after failing to co-operate with Nazi troops.

Years on, Caligula's producer Bob Guccione and stars McDowell and Mirren

Although the BBFC insisted there was no evidence that the film caused harm to viewers, its decision prompted calls to make the body directly answerable to Parliament.