When Philippe Sands was growing up, the Holocaust loomed silently over his world like an unwanted visitor who won't leave. "I've lived with it my whole life," says the eminent barrister, when we meet to discuss his role in the thought-provoking new documentary, My Nazi Legacy, which is showing at this month's Jewish Film Festival.
"I grew up in a household in which we didn't have German things. My brother and I knew there were things that had happened but, like many families, we never talked about it."
Sands's mother was born in Vienna and survived the war as a "hidden child" in France. She claims to remember nothing before 1945. His grandfather, who was born in Lviv in western Ukraine, never spoke about the war or where he came from. Sands later discovered that he was the only survivor in a family of 80.
"So there was no talking about it, but it's there. And it's a big issue. And it informs and it affects you, and I'm sure it affected the career choices that I made."
Last year, when filming the documentary with director David Evans, Sands found himself in a waterlogged field in Ukraine where the remains of most of his grandfather's family and of hundreds of other Jews still lie - where they were murdered - to this day. With him were Horst von Wachter and Niklas Frank, the sons of high-ranking Nazis Otto von Wachter and Hans Frank, whose implementation of the Final Solution wiped out the Jewish population of Lviv and its surroundings in 1942.
The trio had already visited a former parliamentary chamber where Hans Frank gave a speech in which he praised Otto von Wachter for making many of Lviv's Jews disappear; and the imposing disused synagogue where Sands's family worshipped which the Nazis set on fire. Their next stop brought him face to face with current Ukrainian Nazi sympathisers at a chilling commemoration ceremony for the Waffen-SS Galicia Division - the first SS unit to enlist foreigners - created by Horst's father.
The men's lives converged after Sands became fascinated with Frank's father - "He was highly intelligent, highly educated; how could someone take the direction he had taken?" - while researching a book due to be published next year, East West Street: On the Origins of Genocide and Crimes Against Humanity. He wrote to Niklas after reading his acclaimed book about his father Hans, In the Shadow of the Reich, and they met in Hamburg, where they talked for hours. While Niklas bitterly distanced himself - psychologically, emotionally, morally - from Hans and his crimes, he told Sands: "You should meet my friend Horst. They're not all like me."
In the film, Niklas takes out a photograph of his father after he'd been hanged for mass murder at Nuremberg. (He keeps it as proof to himself that he really is dead, but also to remind Germans about what can happen when civil society breaks down.)
Horst also shows Sands photographs, but the mood is different. Horst feels no anger towards his father, just love and devotion. It was the system that was wrong, he says.
Unlike Hans Frank, von Wachter was concealed with help from the Vatican, and died before he could be brought to justice. If he had gone to Nuremberg, he would have been acquitted, Horst insists. "Who would speak against him," he asks Sands, rhetorically. "Only the Jews."
When Sands visited Horst for the first time, the Austrian and his wife were living in three ground-floor rooms of their crumbling Gormenghast-like schloss. "It was bitterly cold and he's broke," says Sands. Horst kept his father's library on the third floor, and the photograph albums he produced astonished the lawyer. "You open them and there's Goering and Goebbels and Himmler and 'AH' [Adolf Hitler], and incredible images."
One day, Horst took a black book down off a shelf. "It was Mein Kampf and it was inscribed by his mother. She'd bought it as an engagement present - 'For our struggle.' So he lives with it and he'll say, 'That's interesting. I didn't know that I had that.'"
Neither Horst nor Niklas hid anything from the film-makers, and even agreed to open up their dialogue in a live discussion at the Purcell Room in London last year, which forms part of the documentary. The men respectfully held their positions without any major fireworks. And it wasn't until near the end of the debate, when Horst proudly revealed that his father is venerated in the Ukraine, that the film-makers knew where to go next.
"After the Purcell Room, Horst said, 'well, if we're going to go to the Ukraine, let's go on commemoration weekend and I'll introduce you to all these lovely people.'"
During the trip, Sands becomes increasingly impatient with Horst's refusal to recognise his father's guilt. In a key scene, he presents him with a document proving Otto's involvement in mass murder and is rebuffed. "His reaction irritates me," says Sands, "and I lose my rag." He admits he's "uncomfortable" with the scene. As a barrister, you're "trained: don't show your emotion, stay cool, be balanced. I'm a lawyer and I'm a human being and there are points where one can no longer be excluded with the other."
Although he never succeeded in eliciting an acknowledgement from Horst, it was important to him to keep trying because "there's a concern that, in failing to acknowledge, you effectively take ownership of what has happened, and that really bothered me."
Their last destination, where newly unearthed remains of fallen Waffen SS soldiers were being buried in a ceremony attended by men in Nazi uniforms, is the most troubling. Throughout the film there is a strong sense that the past is pressing against and informing the present, and nowhere was this more explicit. "My big theme in this is, if you suppress stuff, it will come back," says Sands. "It doesn't go away. It's my own family story of my grandfather and mum not wanting to talk about these things and nevertheless it comes back. And I think that you see that in the fields in Ukraine."
The commemoration ceremony was "as shocking a day as I have ever had," he says. Horst, on the other hand, couldn't have been happier. The inner conflict he sometimes seems to be experiencing up to that point appears to resolve itself as his belief in his father's decency is vindicated by Ukrainian military veterans and younger swastika-wearing attendees. Niklas is disgusted. He tells Sands he believes Horst is a full-blown Nazi and vows to break off contact with him.
"I'm pretty careful who I throw that label at," says Sands, who regards both men as victims, "and I say in the film I don't think he's a Nazi . But he's an apologist, and that's really bad."
Does he think, at a time when antisemitism is increasing, that the film is a warning? "Yes, the film is an expression of my own greater consciousness of the seriousness of issues that are out there for the Jewish community but also for other communities. Xenophobia and racism are on the rise, and antisemitism is part of that.
"I think David and I felt strongly that those scenes in the Ukraine were incredibly important. But I think the heart of it is this sense that it's showing that what happened then is very alive today. Things that are deeply buried don't disappear and we have to be constantly vigilant."