How did an unknown young writer get chosen to rewrite the biggest musical of the decade? Stephen Clark explains what happened when Cameron Mackintosh called him in to make "Martin Guerre" a hit

WHEN Michelangelo was asked how he knew when a statue was finished, he said "an angel taps me on the shoulder". When Martin Guerre opened on July 10 the angel failed to appear, so Cameron Mackintosh, Alain Boublil and Claude-Michel Schönberg decided to send him another invitation in the form of a rewritten show. Ed Hardy, the lyricist - unable to further delay a previous commission - wasn't available to complete the work and as a result the baton was passed to me.

As a child in Derbyshire, watching far too many black-and-white films while strumming my 1969 Les Paul custom and dreaming of farewell gigs at Madison Square Garden, I knew how success happened. You sat, in a dark room, scribbling for years, licking the crumbs off chocolate wrappers, waiting for the phone to ring. And when it did, it would be the world's leading producer wishing to hire your services.

The big break. The call that would turn the rags to ermine and the chocolate to champagne. From then on it would be the usual tedious round of stretch limos in swimming pools and drugs in veins.

So after 10 years as a playwright and poet - one of the highlights of which was participating in the Sondheim masterclasses in Oxford, set up by Cameron Mackintosh - having six plays and eight musicals produced in one way or another, learning bit by bit, supported in lean times by my mother and the endless patience and skill of my agent, learning my trade, making mistakes and occasionally money, the call finally came. The big gig.

Martin Guerre had been open for four weeks when I became involved. I had a meeting with Ed, saw the show that night and the next morning presented my first thoughts to Cameron and Alain. My rational, been-in-the-business-for-yonks self was cool, professional and as articulate as I could manage. However, to be in the presence of two men with CVs that read like the history of the contemporary musical, induced the odd bead of sweat and the occasional stutter I could have done without. But the meeting went well. The gig was on.

At the meeting I explained that there were three areas that I felt were crucial to improving the show. Firstly was the need to clarify who the protagonist should be. Although the show is called Martin Guerre it is very difficult to identity with a man who leaves for the war, is replaced by an impostor, and then returns.

The decision the creators made not to fudge the fact that the "returned" Martin is an impostor - thereby not pursuing the "thriller" line as in the films inspired by the same story - made it even more important to explore the emotional journey of the deserted woman, Bertrande. I felt strongly that it should be her show and that her reactions, decisions and growth were where the heart of the piece lay.

Secondly, the relationship between the religious wars raging around Artigat and the central story had to be more closely woven - they had to make a difference to each other. In the show as I came to it, I felt they ran in parallel and until they collided the sparks could never fly. And thirdly there was the need to restructure the first act, so that whatever story we decided to tell would be clear and driven.

No matter how sophisticated the production values, extraordinary the choreography, or mesmeric the lighting, unless the yarn is well woven the audience will never be taken on a journey. The most immediate application of this for Martin Guerre was the need for a new opening number. And so to Quiberon.

A week after my first meeting with Cameron and Alain - in which it became clear that they were already thinking in very similar terms about what the show needed - I found myself in an exclusive health resort on the tip of Brittany (where most of Les Misérables and Miss Saigon was written). Alain, Claude-Michel and myself discussed the show over low cholesterol stir-frys and anaemic puddings. Late one night I crept off to a small bar, drank three lagers and felt like Herod in Mothercare. Anyway it was there that the new opening number, Working On the Land, was born and on reflection perhaps a visit to a health farm was exactly what Martin Guerre needed.

We had to work very quickly, and Alain and I were in touch constantly, refining the new ideas for the structure of the piece. Apart from the need to make the changes to the show as soon as possible, the recording of the cast album was looming and the producers of the record - Alain, Claude-Michel and David Caddick - were anxious that the new material should be on the album or it would be in danger of being immediately obsolete.

But deadlines are potent and in many ways the paucity of time gave us a momentum that was much needed. Within three weeks we were ready to present a restructured first act, three new songs and rewritten lyrics to Cameron and the director, Declan Donnellan.

Before I knew it we were in the recording studio presenting the new work to the producers - and, most importantly, to the cast. There were many times I was writing and rewriting lines for the end of a song while the same number was already being recorded. Occasionally I felt like a cliché from those black-and-white Saturday-afternoon-in-front-of-the-telly films of my youth. Except it was less relaxing.

With the recording complete, our attentions turned to the stage show. Although some of the lyric changes could be put in immediately, a lot of the changes necessitated re-orchestrating, restaging, relighting, etc. For these the show was taken off for four performances.

During these four days the actors rehearsed from morning to night existing on diets that would have appalled the health farm in Quiberon. (I must remember to open a sandwich bar near a theatre where a show is being rewritten.) While the actors strutted and fretted, one of the bars of the theatre was filled with trestle tables where teams of copyists scribbled thousands of tadpoles to be handed straight to the orchestra to play.

Although those four days were extremely fraught, in many ways it was a relief. For weeks the cast had been rehearsing parts of the new show while performing the "old" one in the evening. And to have to spend so much time in rehearsal so soon after their original opening night was an exhausting process. Indeed there were many times the task seemed almost too daunting. So why do it?

Stories matter. They are where we lose ourselves in order to risk other possibilities, where we can escape and play, or confront and confess. We do not listen to stories or watch stories; we join in. And in accompanying the players of that story we meet many sides of ourselves that we can take back to our lives when the playing is over. And the story Martin Guerre involves much that matters - questions of identity and trust, the difficulty as well as the excitement of love, the effect of a community pushed by fear into behaviour that shocks even itself, and the hope for what may happen when the scars have finally healed. But good stories still need to be told well if they are to envelop us. Flair, humour, truth, insight and, in the case of a musical, melodies, harmonies and movement are all tools that must be well honed.

Last week Martin Guerre opened again at the Prince Edward Theatre. I hope very much that among the thousands who will see it in its new form there will be an angel, reaching out to tap us on the shoulder.