Why the documentary must not be allowed to die

Roger Bolton, the producer ofDeath on the Rock, was another. Death on the Rock revealed that the British Government deployed SAS death squads overseas against the IRA, murdering four unarmed people in Gibraltar.

A vicious smear campaign was mounted against the film, led by the government of Margaret Thatcher and the Murdoch press, notably the Sunday Times, edited by Andrew Neil.

It was the only documentary ever subjected to an official inquiry -- and its facts were vindicated. Murdoch had to pay up for the defamation of one of the film's principal witnesses.

But that wasn't the end of it. Thames Television, one of the most innovative broadcasters in the world, was eventually stripped of its franchise in the United Kingdom.

Did the prime minister exact her revenge on ITV and the film-makers, as she had done to the miners? We don't know. What we do know is that the power of this one documentary stood by the truth and, like The War Game, marked a high point in filmed journalism.

I believe great documentaries exude an artistic heresy. They are difficult to categorise. They are not like great fiction. They are not like great feature movies. Yet, they can combine the sheer power of both.

The Battle of Chile: the fight of an unarmed people, is an epic documentary by Patricio Guzman. It is an extraordinary film: actually a trilogy of films.

When it was released in the 1970s, the New Yorker asked: "How could a team of five people, some with no previous film experience, working with one Éclair camera, one Nagra sound-recorder, and a package of black and white film, produce a work of this magnitude?"

Guzman's documentary is about the overthrow of democracy in Chile in 1973 by fascists led by General Pinochet and directed by the CIA.

Almost everything is filmed hand-held, on the shoulder. And remember this is a film camera, not video. You have to change the magazine every ten minutes, or the camera stops; and the slightest movement and change of light affects the image.

In the Battle of Chile, there is a scene at the funeral of a naval officer, loyal to President Salvador Allende, who was murdered by those plotting to destroy Allende's reformist government.

The camera moves among the military faces: human totems with their medals and ribbons, their coiffed hair and opaque eyes. The sheer menace of the faces says you are watching the funeral of a whole society: of democracy itself.