For their eyes only: Inside the world of the film censor

Scenes of unrelenting degradation, torture and sexual humiliation? All in a day's work for the film censors tasked with deciding which of the 14,000 films, videos and computer games submitted each year are unacceptable for British audiences.

The British Board of Film Classification (BBFC) this week took the rare step of refusing outright to classify a new film for release. The Human Centipede II was rejected for DVD with a warning that the horror movie could inflict psychological harm upon viewers.

Normally the team of 16 examiners employed at the Soho Square headquarters of the BBFC, which was established as a body independent of the film industry in 1912, will only suggest cuts to even the most troubling films so that they can be passed with an 18 rating. But examiners found that the film, a sequel to last year's 18-rated Human Centipede, about a mad scientist who grafts three kidnap victims together, failed the so-called "Blackpool rock test".

They said the sequel, which deals with a man who becomes "sexually obsessed" with a DVD of the original film and wants to put the idea into practice, was "rotten" all the way through.

In an email to Empire magazine's website, Tom Six, the film's writer and director, said the rejection was an outrageous act of censorship. "Apparently I made an horrific horror film, but shouldn't a good horror film be horrific? It is all fictional. Not real. It is all make-belief. It is art. Give people their own choice to watch it or not. If people can't handle or don't like my movies they just don't watch them," he wrote.

The ban, reflecting a fear that the film may breach the Obscene Publications Act, is a drastic step from a body that admits it has been moving in a more liberal direction since the "video nasties" scare of the 1980s.

Last year the BBFC cut just 1.4 per cent of films and 2.5 per cent of videos. When a film is singled out for particular concern, the body adopts a strict "refer upwards" policy.

Normally, every film is watched by a pair of examiners. The Human Centipede II was flagged for concern and sent straight to the senior examiners. It was then sent to David Cooke, the BBFC's director, to assess, and with a ban favoured, referred up to the "presidential team", led by Sir Quentin Thomas, whose pre-credits signature of approval is familiar to every cinema-goer.

Despite the popular view of the film censor wading through hours of pornography in a dank Soho basement, the examiners' see much more than the extremities of human behaviour. "We don't have particular experts in sexual violence or torture scenes. Everyone watches a balanced diet," said a BBFC spokesman. "An examiner can become complacent or lose concentration if they see too much of one thing."

Vacancies are rare and examiners have to demonstrate some "experience of life" before joining. There is no mandatory retirement age for the team, who are currently aged between their late twenties and early fifties.

The examiners watch up to 20 hours of material but there is no formal counselling for any traumatic scenes they might encounter. "There's a weekly Wednesday meeting where issues are raised but they mainly talk about things they've seen informally over a coffee in the office," said one insider.

The censors bear "public concerns" about sex and violence in mind, but their judgments must be guided purely by the body's own classification guidelines and the boundaries of obscenity law.

Scenes of non-consensual sexual humiliation and imitable acts of violence raise particular concerns. But the body also banned a 2005 DVD titled High-Yield Hydroponic System for presenting "clear and detailed guidance on the cultivation of cannabis".

Distributors increasingly send rough cuts of the biggest blockbusters to examiners in the hope of avoiding an age rating of 15 or over, which has a negative effect on takings at the box office. Examiners enjoy the peculiar but privileged position of watching the latest Bond film before any digital special effects or music soundtrack has been added.

The Da Vinci Code was sent back to Sony in 2006 with a request to tone down the "crunching" sound of broken bones if producers wanted to secure the 12A rating they desired.

In another wing of the BBFC, computer games experts analyse the latest violent titles. One skilled player handles the controls whilst another keeps a close eye on the screen's visual backdrop while they seek to award the age ratings for games.

As the BBFC's centenary approaches, the body accepts that there is little it can do to stop Tom Six and other directors simply uploading films on to the internet. But it has set up a voluntary online ratings system to which it hopes filmmakers will sign up.

Examiners do sometimes admit to feeling shellshocked at the weekly gathering. "It's not the hardcore pornography and violence," said the insider. "It's children's DVDs – having to watch five hours of Ivor The Engine."

The BBFC has defended its ban of The Human Centipede II. "There is little attempt to portray any of the victims in the film as anything other than objects to be brutalised, degraded and mutilated for the amusement and arousal of the central character, as well as for the pleasure of the audience," it said.