In round-rimmed shades and a scruffy black T-shirt, Peter Zadek looks many years younger than his distinguished 69. He's in Britain to prepare for the Edinburgh opening of his Berliner Ensemble production of The Merchant of Venice, and it's odd to think that this epitome of relaxed internationalism cut his teeth in darkest Wales. He has no illusions about those Pontypridd days: "The miners weren't bloody interested in what I was doing, and there was no reason why they should be."
Zadek at least had quantitative success in Wales; he put on a play a week for a year there. Then, in 1958, after 25 years in Britain, he moved to Germany, where one of the first plays he did was The Merchant. He mounted another one 14 years later, in the industrial town of Bochum. It reminded him of Wales.
"This time I wouldn't make the same mistake - I'd get into the theatre the audience who should be in it. I did a popular revue-type show, which carried the theatre for five years, and gave me the courage to do Shakespeare in a very open and popular way."
His Shylock was the Nazi caricature of a Jew: a long-nosed, rat-like figure shorn of any redemptive features: it was a daring move.
"I discovered that the more horrible you made Shylock, the more sympathy you got from the audience." Zadek calls this "the trick of the play".
The Merchant has long preoccupied Zadek, a Jew and today considered one of the top directors working in the German-speaking world (he has a British passport). Zadek's current production opened in Vienna in 1988. The trick this time has been to make Shylock as un-Jewish as possible.
He is played by Gert Voss, who has become an Edinburgh stalwart over the last three years: he was Peter Stein's Antony in Julius Caesar in 1993, Zadek's Antony in Antony and Cleopatra last year, and is also appearing in a Schaubauhne production of Guitry's The Illusionist this year.
"Voss," says Zadek, "is a good-looking German from Hamburg, with blue eyes. When he does Shylock, you listen to what he says in a completely different way. You realise this is a play about money, revenge, racial hatred - with enormous irony and humour. Those are the strengths of his character."
Zadek's new Merchant depicts a homogenised society where the fastest on his feet, and on the vodafone, wins. Jews are assimilated, not victims.
The scenario stems from Zadek's early childhood in Berlin, where he was born to comfortably-off and completely assimilated Jewish parents. His mother underestimated Hitler's staying power, and had to be tricked into leaving Germany by her husband, a travelling salesman who knew England well.
The Zadeks arrived in London in 1933. Peter was six. He was brought up in Hampstead Garden Suburb and got a languages scholarship to Oxford at the age of 17. Then something very odd happened.
"The scholarship was for Jesus College. But they didn't take me, as their 'Jewish quota' was full. This was at the beginning of the war, note, when the British were fighting the Germans: and many colleges had their 'Jewish quotas'. At 17, you're not clever enough to say, 'Well, if they're like that, I'm not going.' So I did the exam the next year, and went up to St John's."
Zadek was part of a gilded generation: this was the wartime Oxford of Peter Brook, Kenneth Tynan, Richard Burton. Zadek learnt his Shakespeare at Neville Coghill's feet, but never took his degree. The Old Vic directors' course in 1946 proved irresistible.
Over the next 11 years, Zadek worked in BBC Arts under Huw Wheldon, and got himself a name for stagings in what he calls the "absurd area" - Ionesco and Albee. He did a spicy premiere of Genet's The Balcony before its first Paris production - at the Arts Theatre, London, in 1957, and was nearly murdered for his pains.
"Genet didn't like what he saw in rehearsal. I arrived one day to find him sitting on stage with a revolver. He was going to shoot me. He was banned from the theatre, and the show went on to be an immense success."
In post-war British theatre there was probably room for only one enfant terrible called Peter. Brook had made an immediate splash; Zadek was less sure of himself. He didn't want to be part of the refugee world, but didn't fit in with the arts establishment either.
"I tried, but I wasn't good at it. I had a lot of problems, but I'm like that - always looking for round holes into which to fit my square pegs."
Without his family - he had had two children with his first wife - he moved back to Germany, and soon teamed up with a brilliant theatre manager, Kurt Hubner, and designer Wilfred Minks. Zadek still works with the latter, who is responsible for this Merchant set.
Over the next three decades, Zadek's reputation as an adventurous director of Shakespeare grew, particularly at the Hamburg Schauspielhaus, where he was in charge from 1985-89. He also did the first European version of Sobol's Ghetto there, to great acclaim.
In 1992, he returned to Berlin as co-director of Brecht's old company. From here came Antony and Cleopatra as well as a fascinating production of Pinter's Moonlight. But the relationship has not lasted. Zadek left the Ensemble earlier this year in a public dispute with his co-director Heiner Muller over the theatre's "anti-West" political stance.
"Things are very hysterical in Berlin now," Zadek says. "The climate has deteriorated since reunification, not just inside the theatre but all over town. Audiences, young ones especially, are only interested if you shout at them. It's all become extremely propagandistic, brutal and vulgar."
Zadek's sing-song Oxford accent, rather surprising for a man who worked so long in German (he lives in Italy with novelist Elisabeth Plessen), does perhaps recall another theatre age. Yet his star still shines very bright: he is about to direct The Cherry Orchard in Vienna, with a cast he says he's been waiting for for 10 years. What keeps him working?
"All I'm interested in is actors, and stories about people. I don't want to persuade an audience to believe in this or that. With a good production and an audience a thousand strong, there will be a thousand opinions. If those thousand opinions become one, then I'm very unhappy."
n 'The Merchant of Venice', today and tomorrow, Royal Lyceum Theatre, Edinburgh. Bookings: 0131-225 5756