The relentless message is the industrial scale of the mass murder. Footage from the Majdanek camp in Poland shows heaps of victims' personal effects, from eye glasses to suitcases to children's toys.
"It's hard to imagine for a normal human mind," recounts one British veteran, fighting back tears decades later, in an interview for the companion film Night Will Fall.
"I had peered into hell."
The accompanying documentary is the "making-of" story of the Camps Survey, which was started while the battles still raged, but shelved by the British government before the end of 1945.
Night Will Fall tells the story of Sidney Bernstein, then head of Britain's Psychological Warfare Division, who wanted to create "a lesson to all mankind", even enlisting the help of his friend Alfred Hitchcock.
Bernstein "anticipated that in the future people would deny the extent of the atrocities," said Imperial War Museum curator Toby Haggith, whose team painstakingly restored the archival footage.
One camp survivor, Croatian film producer Branko Lustig, 81, told the Berlin audience that "this kind of movie must be shown every 25 years, to every new generation".
Some of the footage was used as evidence at the Nuremberg trials, and shorter versions were screened later, but the major documentary envisioned by Bernstein in 1945 was never released.
Director Andre Singer offers several possible reasons, including the shifting post-war focus on the looming Soviet threat, and the need for the Allies to co-operate with the occupied German population.
Haggith said, as the war was over, the film simply "had missed its moment".
He added that screening the footage now would also be a tribute to the cameramen, "the real heroes of the film".
"They were angered by what they saw," he said. "They were shocked, but they also had a great ability for empathy."
Empathy is in short supply in a third documentary, The Decent One, an intimate look at the private life of Hitler's chief henchman, Heinrich Himmler, head of the SS and Gestapo secret police.
It is based on another stunning find, the discovery of hundreds of private letters between Himmler and his wife, children and mistress, as well as diaries, photos and even recipe books of the family.
The documents, dated 1927-45, were taken from Himmler's Bavarian home, likely by US troops, and resurfaced in Tel Aviv decades later, via an unclear route that may have involved a Brussels flea market.
Filmmaker Vanessa Lapa juxtaposes voiceover of the often mundane family correspondence with archival footage, frequently of horrific Nazi crimes.
In the letters, which are also studied in major new newspaper and book projects, Himmler calls his wife Marga, who is seven years his senior and a visceral anti-Semite like him, "my good, pure woman".
She playfully tells him "I am so happy to have such a good evil man who loves his evil wife as much as she loves him".
There are few references to the Holocaust, only allusions including the chilling line: "I'm driving to Auschwitz. Kisses, Your Heini".
What emerges is not a split personality, but the portrait of a man devoid of empathy and fully committed to his cause.
"Heinrich Himmler is not a character like Dr Jekyll and Mr Hyde," Lapa said.
"I believe he is the same person in private as in public.
"Whenever there is a sentence or two where he is seemingly kind, loving, banal, you quickly see the hate again. It's always in there... He is banal, and at a certain point he chose evil."
- AFP
