Diana film detailing 'dark forces' to screen at festival

The screening of Unlawful Killing at the Sydney Underground Film Festival on September 7 and 8 is understood to be the only time it has been shown outside a private screening at the 2011 Cannes film festival and at an Irish festival.

It will be screened one day after the world premiere of Diana, a biopic starring Naomi Watts, in London on September 5.

The underground festival's co-director Stefan Popescu said Unlawful Killing was not allowed to be shown in Britain.

Lawyers had asked the director Keith Allen to make a number of cuts to the documentary because of allegations made about the royal family.

The film claims Prince Philip is a psychopath with a Nazi background, while the Queen and her sister Princess Margaret are described as "gangsters in tiaras".

The film's US release was shelved after insurers declined to indemnify the makers against potential lawsuits in Britain, The Guardian reported last year. File-sharing sites such as YouTube had prevented the uploading of the film or quickly removed it, Popescu said.

The film also questions the impartiality of the coroner who presided over the 2007-8 inquest into Princess Diana and Dodi al-Fayed's deaths.

Scotland Yard is now investigating new evidence, including claims they were murdered by a member of the British military.

Popescu also said there had been a concerted campaign to attack the film's credibility, with the British press focusing on the fact that Dodi Fayed's father Mohamed al-Fayed bankrolled the film.

''Screening this documentary is a gesture enforcing the right to freedom of expression and opinions,'' he said, adding he believed there was no reason to ban the film in Australia.

Roy Baker from Macquarie University's Law School said the festival could only be prevented from screening Unlawful Killing if it advocated terrorism, promoted crime or violence or dealt with issues including sex, drugs and children in a way that seriously offended reasonable adults.

The director of the Classification Board Lesley O'Brien said a decision on whether to permit the screening of the film had not been made.