God On Trial: a new 90-minute drama for BBC Two
Stellan Skarsgard plays Baumgarten
Baumgarten was a sophisticated, modern and successful professor of Criminal Law in Berlin who taught bright, admiring students and obviously mixed in fairly high circles.
It transpires that he was brought up believing he was German – a good, Jew-hating German who knew nothing of the Jewish way of life, only that Jews were dirty, deceitful and dishonest.
He is appointed Head of Court in the trial. He is brisk, confident, demands authority and seems to take control naturally, gaining respect while being kind and fair.
Stellan explains: "Baumgarten was just recently taken by the Gestapo and put in Auschwitz despite having no idea he was Jewish, but he's been there long enough to know the rules.
"It transpires that his father was Jewish but died when he was a child, so he was brought up a good anti-Semite himself."
Baumgarten builds up a fragile relationship with the other inmates: "When you think about the relationships in a place like Auschwitz there were friendships of a sort but they were very fragile because if you wanted to survive you couldn't really afford to have real friends.
"Under those horrible conditions you become more or less like an animal struggling to survive."
Stellan was drawn to the script by the quality of Frank's writing: "It is solid writing not only in terms of it being a beautifully written drama but also in the way it presents the ideas. I like the discussion that takes place.
"In some ways I've been obsessed with this period because it serves so well as a model for us because of how extreme it was.
"I've played Raoul Wallenberg, who saved a lot of Jews, in Budapest in one film and Wilhelm Furtwangler, the German conductor, in a film called Taking Sides, both of which deal with this period.
"It's important in that we have so much to learn from this period in history."
He continues: "We have to try to understand everything that happened under the Nazis in the most sophisticated way and not buy into the clichés.
"It's important to understand that anti-Semitism wasn't invented by them; it had a long tradition in Germany. Martin Luther was anti-Semitic and the church had always been.
"Also at that time people thought that there were much greater differences between races. In the United States for instance, race laws weren't banned until the 1960s, so it was easier to make people believe that the Jews were different and dangerous and this was a kind of witch hunt, a superstition that always has to be fought against.
"That's why we have to keep our heads cleared and be self-critical because it's very easy for a human being to torture or kill another human being; the varnish of civilisation is very thin and we have to take care of that."
He enjoyed the process of filming the drama: "There is a quality that you get when you shoot long takes which you also get in the theatre but rarely in film.
"When the material starts to breathe by itself and you get into a rhythm, your endorphins get to work; you stop being nervous and everyone comes together like a living organism.
"When you work like this you don't rehearse in detail – you just go for it. All those fantastic actors I worked with immediately found a way to play together, like a jazz orchestra that is jamming, which is a really lovely way to work.
"You also get a real sense of freedom when there are three cameras in play; they will find you somewhere and if they don't you do it again and as a job of work it was a delightful experience."
Stellan is used to working with demanding subject matter, and found the camaraderie between the cast members invaluable: "I'm pretty used to doing horrible stuff on film. I like to go to those places and see what it feels like. The subject of the Holocaust is horrifying, but that doesn't mean you can't joke about it.
"You have to get out of Auschwitz between takes. There's no reason to become a prisoner in Auschwitz just because you are playing one.
"I've worked with a couple of the other actors before, but it was a very solid group with great theatre experience and discipline and a wonderful attitude to work.
"What happens when so many good actors come together in an ensemble piece is that we all have the same responsibility so start to perform together in a way that I like. I much prefer that. I don't like doing monologues and solos; when you have give and take I couldn't be happier."
Stellan hadn't worked with the director, Andy de Emmony, before: "He was brilliant. He managed to pull more than 20 actors and some 30 or 40 extras together.
"It was very concentrated and Andy created an atmosphere so that as we got ready to turn over you could hear a pin drop. He never raised his voice but just walked around and spoke very quietly to those he wanted to and then we went for it.
"He created a very relaxed atmosphere which meant there was an enormous focus when we shot."
Stellan adds: "I'm not myself a believer, but I think it's important we continue to have discussions about morals and responsibility whether it's God's responsibility or our own.
"I think that most religion is just superstition and sometimes equally dangerous. Before 9/11 I was more agnostic; I didn't really care about religion.
"My attitude was 'Well, if there is a God and he's good, then he will see to my deeds and if he wants me to worship him then he's too vain to be worthy of my worship.'
"But after 9/11, when the leader of the most powerful nation in the world said that God placed him as the president, it became a little harder to be neutral on religion.
"Also the people that flew into the Twin Towers had their idea of religion. I've read the Koran and I've read the Bible and I find them pretty frightening.
"I think we have to continuously fight superstition and we have to be really careful about making sure we question ourselves and our ideas all the time. Uncertainty is a beautiful thing."
He concludes: "God On Trial is a very thrilling discussion and it's very smartly written – and when you listen to it you feel smart yourself and maybe come out of it feeling a little smarter."