Ken Stott found himself genuinely disturbed by his latest role. "It invaded the rest of my life," the actor sighs. "I had terrible dreams throughout the period I was playing this character. I remember lying in bed, shivering and tormented by bad dreams, on dark, cold, windy nights. Such was the weight of this character, I felt the spirits of those who had been around him coming back to haunt me." The rugged, craggy-faced Scottish actor is a veteran of such gruelling series as The Vice and Messiah - but playing Adolf Hitler is clearly more punishing even than that.
The 49-year-old Stott portrays the Führer in Uncle Adolf, the latest take on the Nazi leader, on ITV1 on Monday. But Hitler has, of course, been depicted on screen before, by actors as diverse as Charlie Chaplin, Robert Carlyle, Antony Sher, Noah Taylor, Ian McKellen, Frank Finlay, Alec Guinness, Anthony Hopkins and Derek Jacobi.
It is no surprise that film-makers keep returning to this figure: he may have been one of the most reviled men in history, but Hitler shaped the course of the last century. "It is sad but true that he defines the 20th century," says Mark Pybus, the producer of Uncle Adolf. "In the Second World War, humanity totally lost its innocence - and the modern world as we know it today began. That's all down to Hitler, and it's why we keep going back to him."
For all that, one aspect of the Führer's life has been little explored on screen: his obsessive, almost certainly incestuous, relationship with his niece Geli, who was 16 years his junior. Uncle Adolf charts the details of this previously little-covered affair - and it offers a compelling insight into the psyche of the Nazi leader. Scripted by Nigel Williams (who wrote The Wimbledon Poisoner, Dirty Tricks, and Bertie and Elizabeth), the film suggests that Hitler's fixation with his niece became so oppressive that it eventually pushed her to shoot herself with his gun.
Geli, played here by the Irish actress Elaine Cassidy (who has appeared in Felicia's Journey, The Others and The Lost World), committed suicide in 1931 at the age of 23. Geli's death served to make Hitler even more driven - and coloured his attitude to the world and women in general. Subsequently, he would tell supporters that he was "married to Germany", and conducted a cold, formal relationship with Geli's rival, Eva Braun (Christine Tremarco), the woman he wed just before their deaths in the Berlin bunker in 1945.
That bunker is where the film opens. The dishevelled Führer sits alone in his private viewing room, watching home movies of himself and Geli over and over again. In the flickering footage, he is happily pushing his niece on a swing, and they are laughing together. In the present, however, Hitler is seriously ill, popping pills with shaking hands. He has turned his bedroom into a shrine to Geli, with a bust of his young niece in pride of place. Bitter and twisted, he snarls at the loyal Eva: "We all need love once. I have only loved once."
Uncle Adolf then spools back to Munich in 1929, where Hitler embarks on his intoxicating, intense relationship with Geli. He chases her round the piano, doing mock-Nazi salutes, and flirtatiously threatens to spank her. Their relationship takes on a darker hue when Geli's light-hearted admission that Hitler's chauffeur tried to kiss her sends him into an incandescent rage. He immediately storms out of her bedroom, grabs a walking stick and beats the sleeping chauffeur to within an inch of his life.
It takes a mutual friend, Hitler's official photographer Heinrich Hoffmann (Peter Wight), to explain to Geli the power that Hitler now exerts over her. "You pretend that you're your own woman, but you're his, like the rest of us. At first, you think, 'I want to do this just to please him,' so you do it. But he asks for more, so you do more. Then you realise you can't please him, not really. That's why he will always get what he wants." Exhausted by her uncle's possessiveness, Geli escapes his clutches and starts a secret affair with her Jewish music teacher, Hans (Grant Ibbs). The consequences of this are catastrophic. The aim of the piece is to show how the private is inextricably linked to the public. As the Nazi leader himself asserts in the film, "Everything is political." Hitler bullied and tyrannised Geli in the same way that he later bullied and tyrannised the world.
Puffing on a succession of Gitanes and dressed down in a black T-shirt, Stott is taking a well-earned break at the end of the arduous Uncle Adolf shoot - much of which has taken place in Lithuania in temperatures of minus 20C. The actor begins by declaring that the personal is political. "I'm of the opinion that Geli's suicide had a very big influence on Hitler. It hardened an already determined man into a character who set aside all prospect of meaningful relationships and instead threw himself with missionary zeal into his ambition to create a new Reich. After Geli, he closed down the very idea of personal relationships and became obsessive about his work.
"This relationship seems like a small event when you think of the 21 million Russians or the six million Jews Hitler killed. But in terms of his life and the formation of his character, the relationship was incredibly significant."
Pybus chips in: "When Geli died, Hitler was hysterical and very depressed. At the time, there were veiled references to the fact that he felt suicidal. He saw himself as a tragic hero, and this event played right into that self-image. The days of romantic picnics were over, and he became absolutely focused on what he saw as his destiny. People suggest that, had she lived, Geli might have shaved off some of Hitler's rough edges. I don't subscribe to that view, but you can't help thinking, 'What would have happened if she had shot him rather than herself?'"
The producer continues: "By the end of the film, we learn that the way Hitler manipulated and controlled people in his private life was exactly the same as the way he manipulated and controlled the German political process. His unwillingness to accept that anyone else could have a degree of control led to Geli's death.
"But even then, he never acknowledged that her death was the result of his actions. He brought about terrible destruction and devastation, but there was never any acknowledgement from him that he was the person who had caused it. Till the very end, Hitler remained insulated in this sense of self-righteousness. Everyone else had failed, but he was always in the right. He never learnt in his private life - and that was true of him as a leader as well."
All the same, when you portray Hitler's private life, isn't there a danger of humanising a figure once described by Malcolm Muggeridge as "a psychopath who somehow found his way from a padded cell to Potsdam"? Don't you run the risk- even inadvertently - of making him sympathetic? Stott thinks not. "While Hitler's charm lends him a plausibility - as it does with Richard III - it does not in any way make him sympathetic. In fact, in this drama he emerges as the vile man he was."
The actor readily concedes that some viewers may find this depiction of the Führer's human side unacceptable, but he contends that, in the end, this portrait will in fact add to our understanding of what made him tick. "I am sure we will come unstuck with some people and cause controversy," he admits. "But if we continue to think of Hitler as a two-dimensional monster and deny that he was a human being, we deny our own humanity."
Of course, Stott acknowledges, "in wartime, everyone comes together and you have to have a common enemy. So Hitler was dehumanised and turned into an animal." But he thinks there is a danger in continuing to adopt such an attitude. "I would never warm to Hitler in any way, but it's essential to know more about him. I think we can shed more light on him by knowing the relationships he had. It's important to show his human aspect in order to say that people who are plausible and exciting and charming can become what we know Hitler subsequently became. It's very dangerous just to let it go.
"It's too easy to view these people merely as monsters," he says. "For me, this is an absolutely vital task. It's like a mission to say to viewers, 'For goodness' sake, we have to take people like Hitler seriously because at the time we didn't.' This serves as a warning from history."
Nick Renton, the film's director, takes up the theme, repeating that Uncle Adolf is by no means an attempt to exonerate Hitler. "Some people will not like our portrayal of Hitler because they doubt whether he was really a human being. They think only that he was a freak. But glamorising Hitler never came into the equation. The target was to find this man and show how someone with this horrific, monstrous side could charm most of Germany."
Williams is equally alive to the potential for controversy when dealing with such sensitive subject-matter, but he also believes that it is crucial to comprehend what made Hitler the man he was. "In writing about anything that calls attention to a negative aspect of human life, you inevitably fly in the face of those who simply don't want to think about it. But in order to prevent anything as horrific as the rise of Nazism happening again, one of our most important duties is to understand it.
"I don't think in trying to get at the tiny spark of humanity that lurked within Hitler we are minimising the risk this evil man posed. The truly terrifying thing about him was that he was human. Real monsters don't come with horns and tridents; they look, speak and act just like you and me. That's as true of serial killers as it is of people who murder millions, like Hitler."
Stott concludes by expressing his mighty relief that the filming is now all over. Playing Hitler has clearly taken a heavy emotional toll on him. The actor rubs his now clean-shaven upper lip, from which he has just removed the trademark moustache. "As soon as the moustache came off, the man was gone," he says. "I immediately threw away all the books I'd read for research - I didn't want them taking up room on my shelf. I chucked him away. I wanted him right out of my life."
'Uncle Adolf', 9pm, Monday, ITV1Reuse content