''DO you know,'' says Helen Mirren, ''that this is the first time in my life I've done a movie that's a two-hander with another woman? In my whole career. It's appalling.'' She is talking about her new film, Istvan Szabo's The Door, the story of the complex, often difficult relationship between a Hungarian writer and the woman who cleans her house. The only other film that has come close, she adds, is Calendar Girls, a 2003 ensemble comedy about middle-aged women who pose nude for a calendar to raise money for leukaemia research.
Why should it have taken so long, she wonders, for her to be in a film with two female leads? And perhaps that's one of the reasons why she and German actress Martina Gedeck enjoyed working together so much - they appreciated the sheer novelty of the situation.
The Door, she notes, is in a somewhat different register from Calendar Girls. Mirren plays the cleaner, Emerenc, and Gedeck (The Lives Of Others) plays the author, Magda, whose writing life is shadowed by the politics and censorship of 1960s Hungary. Emerenc, fierce, uncompromising, intensely private, has not let a single person into her house for decades. ''She has buried things deep, because she had to, because they were so full of horror,'' Mirren says. She and Magda form a complicated alliance, shot through with respect, frustration, even hostility at times, full of contradictions to the very last.
Mirren says she found the role ''so difficult to play. One of the hardest things I've ever done. Somehow, you had to channel her, pretending to be her just didn't work, because I didn't want to be seen to be acting.'' She knows, she adds, that she bears a certain burden of familiarity. ''You're carrying the baggage of recognition, which is an advantage for the film in one way, but a disadvantage in another. So being the part, rather than acting the part, was very important for me.''
She also felt a sense of responsibility, she says, ''to a generation I respect so deeply for the terrors and the horrors that they went through.'' Part of her research, preparing for the role, was ''to reinvestigate World War II history. We've almost lost the generation who experienced it firsthand, and these are very dangerous times, because it means that people forget.'' This included a visit to Buchenwald, ''to bear witness, for the first time. I've visited other sites, ghettoes and synagogues and prison camps, but never a place like that.'' She also found inspiration, she adds, in a 2009 Chilean film, The Maid, with Catalina Saavedra in the title role. ''If it had been an English-speaking film she would have won the Oscar. It was there, full and realised, on the screen in front of you,'' with exactly the effortless sense of ''not acting'' she was seeking for The Door.
Szabo, a veteran Hungarian filmmaker - whose films include the Oscar-winning Mephisto, Sunshine, Taking Sides and Being Julia - read the book on which the film is based more than 20 years ago, without any thought at the time of adapting it. It was written by the late Magda Szabo (no relation), a Hungarian novelist, whom he knew well.
For him, he says, film ''is based on human faces. To me, that's the really unique thing about motion pictures, that they show to show the audience the emotions carried by faces.'' It's not an accident, he says, that people form attachments to actors: ''Humphrey Bogart was important for the audience, Greta Garbo was important. People feel that they are represented by peculiar, or powerful, or charismatic faces.''
That's why, he says, he was so happy to do this film with two actors he thinks so highly of. He can't say enough about Mirren. ''This fine, subtle actress, I admire her so much. Acting is a profession, and if you are a good student, you can learn a lot of things, but what Helen Mirren can do, you cannot learn. You are born with this power.''
As a director, he says, it's important his actors know he has only one aim - ''to create the best possible circumstances for a performance, and to put the camera in the best place for the audience to see how fantastic they are. I don't care about interesting camera positions, I would simply like to show their talent, and the story that their faces communicate.''
The Door opens today.