While professional historians have for a long time seen fiction, biography, memoirs, poetry, plays and paintings as respectable sources for their investigations, they have tended to ignore until comparatively recently the potential of film and cinema, and especially that of feature films.
The American historian Arthur M Schlesinger Jr has pinpointed one reason for this attitude, suggesting: "Movies have had status problems ever since they emerged three-quarters of a century ago as a dubious entertainment purveyed by immigrant hustlers to a working-class clientele in storefront holes-in-the-wall scattered through the poorer sections of cities."
But prejudice against films as a second class art form is gradually disappearing among academic historians. The shift has promoted one A-level examining body to encourage the use of film as evidence, and others to consider doing so.
The approach is proving increasingly popular among teachers and students. This was reflected in the immense popularity of a "Film as Evidence" A-level history study day held last term at the National Film Theatre in London, at which Jeffrey Richards gave the keynote speech to some 350 students.
The day was organised jointly by the British Film Institute South Bank Education Department and Lesley Doyle, head of history at Hainault Forest High School in Redbridge. Held in association with the Associated Examining Board, it consisted of talks, panel discussions and workshops.
The AEB's involvement arose because of its pioneering History Alternative Syllabus 673, which allows students to use visual material in the historical method paper, and encourages them to use film among other sources in their personal study.
The syllabus, now being revised, attracted 1,000 students in 1990; this summer three times that number will take the exam. "It goes down very well with universities," claims Peter Callaghan, AEB chief examiner. "They say the students doing it seem more committed to history than others."
It was in the Sixties that historians first began to recognise film as a valid source of evidence in their work. The focus at first was on newsreels and documentaries which, with their real people and real locations, were generally thought to give a truer reflection of contemporary life than any fictional feature film could.
This view is now seen as naive, not least because it failed to take account of the question of authenticity. For example, to satisfy the hunger for dramatic pictures from the battle-front, early film-makers regularly faked episodes from the Boer War and the First World War, some of which have deceived experts ever since.
Later newsreels and documentaries, though authentic, were not necessarily objective. As Jeffrey Richards observed: "What was seen on the screen was selected, shaped and placed there in pursuit of certain predetermined policies. The creators of newsreels and documentaries worked under the same constraints as feature film-makers, subject to interference from censors, sponsors and pressure groups."
Nowadays, he suggested, the feature film is acknowledged as equally worthy of investigation. This applies especially to those made between the Twenties and Fifties, when cinema-going was the principal leisure activity of a large proportion of Britain's population.
"If we are to get to grips with that great intangible, 'the national mood', to see what subjects were dominating the popular consciousness, what attitudes to issues, problems and social structures were being disseminated, it is to feature films that we must turn," he said.
One of the points made repeatedly, and highlighted by the many film clips, was the need to look at a film's context, to ask who made it, when, where and for what reason, why it has survived, and what the audience reaction was.
The questions were relevant to the scene from Love on the Dole in which the police fight hunger marchers. Plans to film Walter Greenwood's classic 1933 novel attacking poverty were twice vetoed by the censors during the Thirties. It was finally filmed in 1941.
Wartime films, so often used for propaganda, need particular scrutiny by the historian. Peter Callaghan showed the finale of Mrs Miniver (1942) - when the vicar exhorts villagers to fight for freedom - and reminded us that Churchill felt the film was worth more than six army divisions.
He also invited the students to consider the historical value of a film such as Dances with Wolves. "It's a fantasy movie divorced from truth. Such contacts with the native American Indians rarely took place," he argued. "But it has value in that it reflects the changing attitude and mentality of the Americans today towards these people."
The study day, which gave the students a chance to discuss excerpts from films as diverse as Thelma and Louise, October, Malcolm, The Kid and Platoon, and hear talks by an animator, an archivist and an actress, was a sell-out. BFI education officer Margaret O'Brien said it would probably become an annual event, reflecting the fact that what Lenin called "the most important of all the arts" has finally gained acceptance as a respectable historical source.
The BFI South Bank Education Department, tel: 0171 928 3232 * Archives:
National Film and Television Archive, 21 Stephen Street, London W1P 1PL. Tel: 0171 255 1444
Department of Film, Imperial War Museum, Lambeth Road, London SE1 6HZ. Tel: 0171 416 5000
Researchers Guide to Film and Television Archives, published by the British Universities Film and Video Council. Tel: 0171 734 3687 Historical Journal of Film, Radio and Television, published quarterly by Carfax. Tel: 01235 555335