As an antidote to the Bard's version - "the portrayal of Shylock offends by being a lie about the Jewish character" - Wesker wrote a play called The Merchant - later renamed Shylock - in 1975. Two years earlier, he had seen Laurence Olivier's "racial caricature" (full of "oi-yoi-yoi") of Shylock in Jonathan Miller's production and realised "not that Shakespeare's intentions were anti-Semitic, but the play's effect was".
This was not just an intellectual response - "I revere Shakespeare and am proud to write in his shadow" - but a gut feeling. So in Wesker's version, which is a new play and not an adaptation, Shylock and Antonio are "old friends, not antagonists". But, when Antonio is in trouble and Shylock wants to lend him money, the laws of Venice force them to enter a legal bond.
They decide to make it a "mocking bond", and the penalty of the "pound of flesh" is meant as a grim joke. The tragedy for both is that the law takes it seriously, but at the climax of Wesker's version Shylock does not "rant against not being allowed to cut his pound of flesh", but is overjoyed at not having to kill his friend. "My play," says Wesker, "is about the bonds of friendship, not about bonds for usury."
Born in 1932, in Stepney, east London, Wesker is the son of East European Jewish communists. He explored this background in his epic trilogy of plays - Chicken Soup with Barley, Roots and I'm Talking About Jerusalem (1958-60) and went on to write such classics as The Kitchen and Chips with Everything, which is currently at the National.
Yet despite the huge acclaim for these works, Wesker says, "I always hoped that Shylock would be my best play." At first, his optimism seemed justified. The National read the play and New York beckoned. Then began a catalogue of rejection, disaster, betrayal and sheer bad luck, which is the subject of Wesker's gruelling and compelling new book, The Birth of Shylock and the Death of Zero Mostel.
After rejection by the National, Shylock was put on in the US by John Dexter - "an old friend and collaborator" - with Zero Mostel, an actor best known for his performance alongside Gene Wilder in Mel Brooks's classic comedy The Producers. Because of Mostel's fame, advance bookings of $2 million were reported. Then disaster - after only one preview performance, Mostel suffered a heart attack and died.
With the lead role taken by an understudy, the play ran for five weeks in Washington and, after being savagely cut (without Wesker's permission) by Dexter for Broadway, closed in New York after 10 days. Further attempts at staging it have met with mixed results.
Is Wesker's book about Shylock a personal exorcism? "Partly yes, " he says,"partly I wrote it because it makes a good story; but mainly because it's a book about theatre written in a way that very few people write about the subject." Based on his diaries, Wesker's book gives a behind-the-scenes account of how roles are defined and cuts in the text negotiated during rehearsals. It also shows the pressures and problems induced by producers, publicity agents and actors.
After detailing his unsuccessful attempts to put Shylock on in London, Wesker ends the book on a question: "Why is there such resistance to my play?" When asked about this, he allows himself a sigh: "I have been loathe to believe in conspiracies, but I can't explain the resistance to Shylock, except by saying that perhaps the heads of the major theatres in Britain feel it is an affront to them."
According to Wesker, the theatre establishment says, "Tamper not with Shylock the icon, we need to have the pleasure of forgiving the bard's Semitic villain, but he must remain a figure of hate." Wesker's Shylock is just too sympathetic a character.
As such, he may find it easier to get on to the syllabus than on to the stage. As a teaching resource, Shylock provokes questions about The Merchant of Venice. "My play," says Wesker, "has counter-arguments to Shakespeare - for example, my Shylock is not a clichd moneylender, but an educated bibliophile. In the original, Shylock and Antonio are at loggerheads - in my play they're friends."
Wesker's version is rich in suggestive themes: "There's the relationship of the individual to the state; parent-child relationships (Shylock and his daughter Jessica); and the role of women is important - in my version, Portia doesn't have
to disguise herself. She's a proud, educated, Renaissance woman. There are all sorts of levels on which my play can usefully be studied."
When did Wesker first realise Shylock could be used in the classroom? "I didn't write it as something that could be taught in schools, but once it was finished, I began getting letters from students who studied the play and found it clarified issues."
After Methuen brought out a student's edition in 1983, this feedback increased. Some incidents stick out. When a New York college did a student production using a black actor to play Shylock, "one of the students wrote to me and said: 'If only I had known this play when we were taught The Merchant of Venice at school. I'd always had a feeling that something was wrong with the Shakespeare, now I've got arguments to use against it.' "
At the Hay-on-Wye literary festival in 1995 Wesker was approached by some English teachers. "They came up to me and said: 'We have to teach The Merchant of Venice as a set book, but we're now going to teach your play alongside it.' I was absolutely delighted. I just said: 'Spread the word.' "
Students also had an input into the way Shylock was written. In 1974, at Colorado University, Wesker asked students to comment on Shakespeare's play and "think about my approach and see if it was both plausible and justified". One of them - Lois Bueler - made the "decisive discovery" that Venetian law demanded that no citizen could have dealings with a Jew unless a contract existed. Hence the need for a bond, even if Shylock and Antonio are friends.
When dealing with Shylock, it's difficult to shake off personal memories. Wesker still remembers how, "when my son was about 15, he was called a 'Shylock' at school. I don't think he even knew what it meant." Incidents such as this - and the fact that "I still hear stories about how you can tell if someone is a Jew: by throwing money on the ground" - confirm Wesker's feeling that anti-Semit ism has to be contested.
At the start of The Birth of Shylock and the Death of Zero Mostel, Wesker quotes John Gross's Shylock: Four Hundred Years in the Life of a Legend (1992): Shylock "belongs inescapably to the history of anti-Semitism . . . the result is ugly. The ground for the Holocaust was well prepared." He says, "I agree with him that Shylock has contributed to the negative image of the Jew."
But doesn't Shakespeare give Shylock that wonderful speech - "If you prick us, do we not bleed?" - about being human? "Well, the so-called defence of Shylock," says Wesker, is Shakespeare's "dramatic instinct for not making the opposition too black. It lets an audience come away with its prejudices about the Jew confirmed, but with an easy conscience because of that noble plea for extenuating circumstances. "
Nor is anti-Semitism just a Renaissance phenomenon. One of the subtexts of Chips with Everything, Wesker's 1962 play about national servicemen, is his mixed feelings towards the working class. "I'm ambivalent towards the working class. It's in the blood. My mother was a communist, and was torn between love of the workers and suspicion of their propensity to racial prejudice." In Chips with Everything, the public-schoolboy Pip "says to the working class conscripts: 'You're better than you think you are - and you're much better than your officers want you to be.' This is me saying that I really want a more educated working class - otherwise they're too easily led, too easily exploited."
With education topping the Blair agenda, what does Wesker feel about the future? "I'm hopeful. In 1992, I contributed a letter to Neil Kinnock in a collection called Dear Next Prime Minister (Bloodaxe Books), in which I said that education has got to be top of the list of changes. Now this is finally coming about, I'm glad."
All that remains is to find a theatre willing to put on Shylock in tandem with The Merchant of Venice. Until then, "My play is simmering; I'm waiting for someone bold enough to take it on."
Arnold Wesker's The Birth of Shylock and the Death of Zero Mostel was published by Quartet Books yesterday. #163;12. Chips with Everything is in rep at the National Theatre