You can hope, but I don't think you can plan for it. That would be dangerous," says wise James Bierman about success.

Bierman knows a lot about the subject. As executive producer of the Donmar Warehouse he oversaw and was largely responsible for the theatre's greatest era - a period so great that it even overshadowed Sam Mendes's tenure in the job, and Mendes managed to persuade Nicole Kidman to appear at the 250-seat Covent Garden venue.

Those heady days seem relatively tame compared to the heights reached by the Donmar under Bierman, and the artistic director Michael Grandage.

So why in the name of the theatre gods is Bierman leaving what for many is the most successful theatre in London, possibly the world?

"Good question," he says of his decision to take up a similar job at the Almeida Theatre in Islington. Instead of a direct answer, he prefers to look back at the series of stunning productions during his five years at the Donmar.

It's cynical to drop a Hollywood star into a play and sell it off their back

"When I first came to the Donmar, Michael's plan was to create an identity of what a Donmar show is. A Donmar show didn't have to be at the Donmar. It just had to have Donmar qualities."

So what are Donmar qualities? Art combined with A-list celebrity would be one definition. When Bierman joined forces with Grandage in 2005, the Donmar had already taken a bold step in that direction with their West End production of Guys and Dolls starring Ewan McGregor. But when in 2008 McGregor later returned as Iago opposite Chiwetel Ejiofor's Othello, the wild, award-winning success of that show led to some stinging criticism.

"People said we do this work that everybody wants to see, but no one can get in to see it,", remembers Bierman. "It really rankled. But we took that hurt and used it to create something new."

In the theatre's offices the plan that Bierman put in place was known as "Donmar Big". To the press and public it was called Donmar West End, and it featured four of the biggest names in theatre or film, each of them playing great roles, in productions staged in bigger West End venues.

The extraordinary season started with Kenneth Branagh's Ivanov, then came Derek Jacobi's Malvolio, Judi Dench's Madame De Sade and Jude Law's Hamlet. You can see why Bierman and Grandage, who has also announced that he is moving on, would think Donmar West End would be a hard act to follow. Yet follow it they did with Red, a terrific play by John Logan about the Jewish New York artist Mark Rothko with Alfred Molina in the title role.

In 2010 the Broadway transfer of that play won more Tonys than any other production, with six awards, including the most coveted best play accolade.

"You're only as good as your work," says Bierman. "If the work falls off the radar, the theatre falls off the radar."

You could say that compared to the Donmar, that is exactly what has happened to the Almeida. The North London theatre is still a by-word for quality drama, but has in recent times been overshadowed by the Donmar.

Bierman, who is teaming up with the Almeida's director Michael Attenborough this month, does not see it that way.

"I think what happens is that you have your time in the sun. The Almeida has always struck me as a fantastic place to work and Mike Attenborough as one of the most gorgeous people to work with," he says.

"When I first came to London in 1992, the Almeida was the leading theatre. They had directors such as Nicholas Hytner and Michael Grandage and they had Ralph Fiennes - it was phenomenal. And in time to come the natural cycle will see the Donmar go more to the background, as did the Royal Court who are now the big thing again."

Much of Donmar success has come by way of phenomenon that not all theatre observers see as a good thing - celebrity casting. These days it is harder than ever to get a play on in the West End without a huge star attached to the production. And stars are rarely committed to a play for long periods. Sometimes they just want to beef up their CV.

"When Madonna came to the West End, it sold out, but whether she could act or not was secondary" admits Bierman. "You have to weigh lots of factors - whenever I have approached a star, it has always been an actor who can act. It's cynical to drop a Hollywood star into a play and sell it on the back of them being in it. Jude Law is an actor. He was plucked from the stage to do film. Coming back to do Hamlet was a massive risk for him, but it was something that his actor's integrity wanted to do.

"But there are still productions where the play is the event. When I transferred Frost/Nixon, it was the play that got sensational reviews." When Bierman talks about theatre it is often in producer-speak with phrases such as "mission statement" and "five-year plans".

But this banker's son is clear that what made him a successful producer is not so much a head for figures but a past as a struggling actor.

After graduating from Portsmouth he studied at North London's Central School of Drama. But the work that followed - acting in education programmes in schools - was a far cry from the life he had envisaged.

"It was work but you have to be a particular kind of person to be an actor. Most people define themselves through their work and most actors are out of work. After four or five years I decided it wasn't for me."

He took a job working for legendary producer Michael Codron in the box office at the Aldwych Theatre. It was only meant to be temporary and to pay off a few debts. But Bierman ended up running the operation.

"It was fantastic working for Michael Codron for eight years," he says. "He saw in me something he could develop and I ended up being general manager of the Aldwych."

The experience as a failed actor could not, says Bierman, have been better preparation for life as a producer. "I wouldn't swap any of my CV for anything," he maintains. "It's given me a grounding for most situations I'm thrust into. I understand what it is like on stage as well as off."

But does that mean there is a yearning for the limelight that all actors have and which his case is destined never to be satisfied? Producers the unsung practitioners in theatre, with little public recognition to show for what they do.

Bierman, however, seems content with his backstage role, and cites a recent memory as proof.

"It was a phenomenal night going to New York and winning six Tonys for Red," he says.

"There wasn't one award that I went up to collect. But what was important was that this little theatre had gone to New York and won. I don't want the success for me - I want it for the theatre."