Potsdamer Platz. The Berlin Film Festival is in full flow. Streets swarm with beautiful people striding through slushy snow, plastic identity badges dangling around necks. I am due to meet the German baritone, Thomas Quasthoff. His hotel is crammed with delegates holding urgent meetings, scuppering any idea of us finding a quiet corner.
This is worrying. Establishing a rapport with a stranger while being jostled by film crews is hard. But Quasthoff, too, requires privacy. He is a Grammy-winning musician who has spent the post-prize year fending off journalists. In addition, he is physically unmissable. He was born in Hildesheim in 1959 with malformed arms and legs, his mother having taken Thalidomide during pregnancy. He has the full-size torso of a big man but is, at a guess, a little under four feet tall.
He turns up with a friend, a lawyer.
His lawyer? "No, thank God, I've never needed a lawyer. Except when I was born " I say that in Britain, the 1979 Sunday Times Thalidomide case was pivotal in human rights law.
"In Germany, the lawyers were less successful," he replies, bluntly.
Having seen Quasthoff on stage, I am aware of his capacity to hold an audience as much through force of personality as beauty of voice. In the street, as he heads off to find somewhere less noisy, voice booming, people sense his presence and make way. I'd heard he was moving to Berlin, I shout above the roar of traffic. "I am moving here to marry my former wife and be with our little girl so she can go to school here."
This is news. Nothing I had read suggested a wife or child. "A little girl," I repeat, making sure I haven't misheard. "No, she is not mine, she is my girlfriend's." By now we're in a thronging bar. Several misunderstandings later we establish that he means "future", not "former" wife.
His fianc�e, Claudia, is a journalist from Leipzig. Family life is Quasthoff's new preoccupation. Ask what he thinks about beyond music and he says "love". He will cut back on concerts abroad always a sell-out, he reminds me to accommodate this change of circumstance.
That Quasthoff has a career at all was never a given. He was prevented from attending music college because he could not meet the entry requirements of playing an instrument. "No comment, it's all been said. There's nothing more. Finito," he snaps.
His abrupt manner takes some getting used to. His English, though impressive, is not fluent, pushing him into linguistic extremes. "It's ridiculous," or "It's disgusting," are favourite expressions.
He continued taking private singing lessons while studying law, building up a concert career and developing a taste for jazz (he plans a CD of songs with a jazz ensemble next year).
Everything changed in 1988 when he won the high-profile ARD Prize in Munich. "That was the start of my being known by a wider circle. Eventually I decided I was ready for opera. Many people had said I should try: Claudio Abbado, Daniel Barenboim. I wanted, first, to establish myself so that my artistry would be more important than my physical disabilities. I know I don't look like Alain Delon but I'm good enough musically.
"The fuss about what singers look like is disgusting. Was Margaret Price ever thin? Was Jessye Norman thin? No, never. No one thinks Deborah Voigt looks like a straw, but if a dress doesn't fit her, make a new one. I've worked with her and she's a wonderful artist. The way she has been treated [by Covent Garden] is disgusting. Disgusting."
It was Simon Rattle who, in April 2003, persuaded Quasthoff to break into opera as Don Fernando in Beethoven's Fidelio with the Berlin Philharmonic. A year later he played the mortally wounded Amfortas [right] in Wagner's Parsifal, repeating the role last month.
"I work with the most hated conductor in the world, or so you English seem to think. What you say about Simon is disgusting, ridiculous. Why does everyone write such hateful things? Are they jealous? We have an expression, a prophet always has biggest difficulties in his own land. He is an incredible person, a superb musician and now, too, he is happy and balanced with his girlfriend Magdalena [Kozen�]."
And what does Berlin think of Rattle? "Generally they love him here. But in Germany, too, there is a tradition: if a head is going up through the clouds, there is always an animal which will try to push it back down."
Unstoppable now, Quasthoff switches to music education. "A cultured population is better than an uncultured one. In Britain it would be more useful to invest in music than in wars. This Iraq war is the most stupid, incredible, dumb project that the British Government has ever been involved with. Would you want to have to tell a mother her son died because of a war which is a lie? But Bush is doing it, and Blair, too. I'm very proud of my Chancellor for saying we wouldn't enter this war. So now you know my politics, too. I'm a red one, an old socialist. A really big artist can never be Nazi. And as for Israel's attitude to Wagner, it's disgusting. Is it his fault he was misappropriated by the Nazis? Everyone was anti-Semitic in his time."
He launches a furious attack on members of the Knesset who walked out recently when President Kohler addressed them in German, adding that he speaks as one who would not have survived the Nazi regime. Then he asks why Palestinians and Israelis can't learn from history. "To come through a conflict and build a wall? Excuse me, Germany showed it is impossible to do this."
He detests the tendency to use the past as an excuse for present behaviour.
"I was once on a talk-show with other Thalidomide survivors. Someone in a wheelchair behaved so disgracefully I said I would kick him if he didn't stop. He's a lawyer, and he's still fighting for compensation. But his behaviour was bad. He ordered his mother around and I said, 'Why do you treat your mother like this. Don't you think she has suffered 40 years of guilt and now you talk to her like this. Are you crazy? You have money, a profession. What more do you want?' "
It is hard not to be shocked by Quasthoff 's candour. But he speaks with a glint of humour. "By the way, Tony Blair knows me personally. We sang together."
"Yes, I was performing at the G8 Summit in Cologne six years ago. Later we had dinner, Bill Clinton, Schroeder, Chirac, me. We were on the alcohol. There was a scene, you cannot imagine we were all sitting on a bench in a hotel bar. Tony Blair's wife was sitting on his knees. And then we all sang, gospel or barber shop, I don't remember. It was really funny."
He grabs my tape recorder and improvises spicily. "Now for the details. Tony Blair was naked. And they were all climbing on top of each other."
Thomas Quasthoff grabs his coat with his teeth and swings off into the night, still chortling.
Thomas Quasthoff performs Mozart at the Barbican on 11 March. Information: [+44] 0845 120 7550; www.barbican.org.uk.