The hell of the Holocaust rises again in this remarkable account of how Britain’s army film unit commissioned producer Sidney Bernstein to make a documentary record of the Nazi death camps, using horrific footage pouring in from the liberation of Belsen, Buchenwald, Dachau, Auschwitz and elsewhere. He employed Alfred Hitchcock as a supervising director. Yet the film, austerely entitled German Concentration Camps Factual Survey, was never completed: Bernstein was stonewalled by political authorities nervous of the growing Zionist movement and in need of Germany as a postwar anti-Soviet ally. In the end, the Americans used some of the footage for a much shorter, punchier propaganda film under the forthright direction of Billy Wilder, rather different to the grieving meditation on inhumanity that Bernstein conceived.

The original project has now been completed by scholars at the Imperial War Museum and will be shown at the forthcoming London film festival, and the story of its genesis is a true nightmare, showing images which I have certainly never seen before. It exposes once again the obscenity of Holocaust denial. This is an extraordinary record. But be warned. Once seen, these images cannot be unseen.