And asked about this, Von Trier - for the first time - lets the wind-up routine and the soundbites go.He says it was never secret, that they got her permission according to the rules of her contract - it was only later that she said no, at which point they stopped filming her. What really annoys him, however, is that it now looks more than likely that the director of the documentary is going to have to take out the bits that she was in Which will, of course, leave a lot of holes. Clearly, Von Trier feels Iceland's righteous little pixie should be more honest about her legal clout. But there's more to it than that."We really disagree about this," he exclaims with a sigh "I was fed up with all this secrecy when I was younger. All this need for secrecy in art - it's about making yourself more mystical, and more fantastic, and making other people the opposite. I understand her point of view (it seems even mentioning Björk's name has become painful to him), she thinks that you shouldn't talk about the religious act. You're supposed to think everything happens as a result of divine inspiration, but that's so wrong."All of which heretical claims for openness sound very impressive, until you remember that Von Trier is a born-again Catholic (a religion, surely, which hugs mystery to its bosom).

And has just made a film boasting a deeply Catholic sensibility. Slowly going blind, Dancer in the Dark's heroine, Selma, is tortured by the idea that her son, Gene, will one day inherit her disease. To ward this off, she saves money to pay for an operation that will cure him, but tells him nothing about her plans, ostensibly in order to prevent him from worrying. She also keeps the secret of a neighbour, Bill, who wants to hide from his wife the fact that he's broke. She keeps these secrets with a determination that is positively frightening and yet she's seen by almost everyone around her as a wonderful martyr."You don't really like Selma, do you?" says Von Trier with a smile.Well, I say, ideals are fine but I wouldn't want her for a mother. "But that was my mother!" he says, almost choking on a chuckle "My mother was an idealist, a very strong woman. As a child, I had the magic feeling that whatever she said would come true.

But when she died, I found out that my father was not my father. And she kept this secret to protect this man and his family, which must have been terrible for her."He leans his head back on the pillows, getting himself comfy, and it's at this point that I realise why he prefers the couch He's in the mood for spilling secrets. The therapy session has begun.Von Trier's mother was a communist, who had no qualms about "screwing around". But honesty did matter ("I used to ask my mother, 'promise me I won't die tonight' and she would say 'I can't promise you that' "). But for some reason, in this case, she decided Von Trier couldn't be trusted with the truth. She had the affair while she was married to Von Trier's stepfather and only told Von Trier about it when she was dying.He says he wasn't angry with her for taking so long to break the news, then changes his mind "It was very, very stupid not to tell me.