Adam's waiting in the wings

Adam Rayner has spent the past eight weeks "hanging out" with Matt Damon in colourless rooms at the back of the Garrick Theatre. This is his job. He is paid to "hang out", but otherwise to do nothing, to say nothing and, if at all possible, to do no acting. The prospect of his going anywhere near the stage at the Garrick puts the fear of God into his employers and, more importantly, would disappoint and infuriate hundreds of theatre-goers. In short, Adam is a typical understudy - an actor who learns someone else's lines, rehearses someone else's movements, and then stands back and watches someone else take all the glory.

If understudying is an exercise in waiting, then it is a neat microcosm of a career in theatre. The average professional actor spends 99 per cent of his time without work or, more specifically, without the kind of work in which a professional actor should be engaged. Streets, shops and restaurants are crammed with thespians reluctantly serving us, stopping us for charity donations, pointing us in the direction of a golf sale: doing anything, in fact, apart from entertaining us.

Adam Rayner is in the upper echelons of that nervous bunch of waiters known as "actors about to succeed". He has many factors in his favour. He trained at Lamda until last summer, winning himself a notable agent. His exposure to potentially golden opportunities has been far above average, but talent is not always a byword for success in his line of work, and the competition for the best parts is fierce.

In this sense, acting is a gambler's profession. The passage from waiting tables at the Bluebird to the green room at the Garrick can often be negotiated, in both directions, by one quick roll of the dice. It was something like audition number 29 that proved Adam's lucky break. Kenneth Lonergan's off-Broadway success This Is Our Youth had been transferred to the West End, starring Hayden Christensen, Jake Gyllenhaal and Anna Paquin. Within minutes of meeting director Laurence Boswell, Rayner had been offered the dubious pleasure of understudying Christensen.

I have to admit here that Adam and I are friends. We regularly swap notes on our respective ambitions: his in acting, mine in any sphere that will have me. He concedes that being an understudy is neither glamorous nor, in the usual run of events, particularly productive. Generally, you are treated like a shadow, and, despite limited rehearsal time, are expected to turn in a polished performance at the drop of a hat.

He is realistic, though. He knows that only a handful of British stars get to pick and choose the roles they like. "Until recently, I'd have taken any job on offer," he says, "and by that I mean virtually anything.

When This Is Our Youth opened in late March, I watched the first performance. Lonergan's script is diamond-hard and, in particular, the character Warren is drawn exquisitely, a loser with whom we cannot help but fall in love. My eye, however, was drawn to Christensen, playing the mean, cynical, drug-guzzling Dennis. Somewhat against my will, I found his performance, like the whole production, surprisingly magnetic. The part of Dennis is to die for, and I told Adam that he should poison Hayden Christensen. For fear of multiplying his frustrations, I declined to share my real thoughts with him, but it occurred to me that he would make an even more compelling Dennis than Christensen: he has more edginess, a sharper delivery and, dare one say it, even finer features. I wondered which particular roll of the dice propelled Hayden into the glories of Star Wars: Episode II, while Adam - like cohorts of other actors - has had to content himself with fringe theatre obscurity.

With the departure of the feted first cast, an equally impressive and Oscar-laden Hollywood troupe arrived in town, with Matt Damon in the role of Dennis. I tried to convince Adam that being Matt Damon wasn't everything in life. "Yeah," he smiled, quick as ever, "because, after all, beneath the handsome exterior, and the burgeoning wealth, and the universal adulation, and his humility on top of it all ... what is there, really?"

I watched Damon's first performance. He fluffed his lines twice. Summer Phoenix and Casey Affleck delivered credible, mature performances and, at times, created an affecting chemistry together. But Damon seemed too soft around the edges, too nice, to convince us that he has the capacity to hurt his friends. I m totally high on fear, he gushed, leaning on the back of a chair, looking and sounding too much like the clean-cut Harvard scholar he once was.

And then, out of nowhere, and in a manner that undercuts the supposition that huge stars can determine their own fate, Damon is told by his studio that he must return to the States for at least seven days at the end of this week. Rayner can't believe the dice. "I'm totally high on fear," he joked, in a New York accent which is, scarily, more convincing than Damon's. "But I'm going to be crucified. Everyone's going to hate me." Recalling the mob of autograph-hunters outside the Garrick, waiting each day for Damon to emerge, I could only concur. But, star or no star, I for one am convinced that Rayner's Dennis will be the pick of the bunch. If Lonergan, and the producers at the Garrick, and the theatre-going public, want quality over razzmatazz, then that's what they're going to get.