Simon Russell Beale: Ah, we've been expecting you

The theory goes that if you want something done, ask someone busy. And there's nobody busier on the London stage than Simon Russell Beale, the man who thinks nothing of rehearsing one play during the day and performing another at night – the lead part in each, of course. So it's no surprise to learn that the 49-year-old actor, frequently hailed as "the best of his age", is one of the stars marking Chekhov's 150th anniversary with a series of readings at the Hampstead theatre all this week. Miriam Margolyes, Rosamund Pike, Michael Frayn and David Hare are among those raising money for the playwright's former home in Yalta, which, as this newspaper first reported, is in dire need of funding as neither Ukraine nor Russia is willing to maintain it.

Moments before I leave the office to meet Beale – the Russell is "false", he later tells me, a necessary addition for Equity reasons – a high-profile colleague is less than glowing about him. The charge is that he does too much: he hogs all the good parts, stopping younger talents from shining. There is, perhaps, some truth in this: Beale is everywhere. On the radio, as George Smiley; on the telly, playing anyone from Napoleon (in Blackadder) to a memorably spineless Widmerpool in the BBC's A Dance to the Music of Time, for which he won a Bafta.

But most of all on stage: in 20 years he has played nearly every major Shakespeare character, Hamlet, Macbeth, Iago, Cassius, Benedict – the lot.

"Yes, I'm a workaholic," he admits in the shabby lavatory-sized room we're shown into backstage at the National, where he is due to start rehearsals for London Assurance, a 19th-century comedy by Dion Boucicault, opening in March. For someone so prodigious, the past two months have actually been relatively fallow. Today, for instance, he has only done one job: a spot of recording at the BBC for Radio 4's 20-hour dramatisation of John Le Carre's George Smiley novels. "I bumped into Jonathan Ross in the lift," he says. "Didn't know me from Adam."

Self-effacement is typical Beale, though, as this story suggests, it doesn't always ring true. Interviewers have remarked on his self-loathing and insecurity, but the older man is different. One of the greatest boosts to his confidence came, aptly enough, from Chekhov, to whom, in a way, he owes his career.

He was in his late 20s when he discovered Russia's Shakespeare, not having studied him at school or university. The moment came when he was cast as Konstantin in Terry Hands' 1990 production of The Seagull, and, in an epiphany, he found he could "do serious". He was thrilled to find he could play more than just the foppish clowns as directors usually cast him.

Chubby, chatty and gay, it's not hard to see how Russell Beale would be in permanent demand for Restoration comedies. As Chekhov's Kostya, the moody young writer frequently compared to Hamlet, Beale delved to depths neither he nor the critics knew he possessed. "It was one of those productions that just changed your life," he says. "It really hit home for me. I absolutely felt Konstantin: he is a miraculously complete part to play. But in careeristic terms I remember somebody said, 'you can do something other than be an idiot'."

Comical parts appeal to him again now, and, in fact, his part in London Assurance is as yet another fop. But it's a testament to his versatility that when one pictures Simon Russell Beale in one's head, he is just as likely to be playing Hamlet as a buffoon. Far from being typecast, he enjoys a range that many actors would kill for.

Admittedly, his big break could have come earlier, a noticeable missed opportunity being when Adrian Noble auditioned him for the title role in Henry VI. After three days the part was handed to a then unknown actor called Ralph Fiennes. "That was the first time I heard of Ralph," he chuckles with a hint of stage jealousy. It must have been galling, I say, to be pipped by a younger and better looking actor? "Yes of course, I was very hurt," he says in a rare burst of emotion, "but Ralph was absolutely magnificent." Looks are, of course, crucial for an actor. Beale has been called ugly and plain, both of which seem slightly unfair, but the most frequent remarks are about his weight.

Does that hurt? "Well it used to a bit. I mean it doesn't really now." He trains twice a week and has recently taken up boxing, which he loves, but he doesn't deny his weight has been an issue, especially when he played Hamlet, aged 40, with jokes about "this too, too solid flesh," quickly becoming a critic's staple. "No, of course I'm overweight. It's happened for 25 years now so you kind of get used to it: I'm actually fat and that's what worries me: as I creep towards middle age I've got to be careful."

He was 49 last Tuesday and has become conscious of ageing, noting there are parts he won't ever play again, such as Hamlet. That role, which he did in 2000, was another turning point: "Someone who had already done it said to me: 'It will change you.' I didn't believe him but he was right. It requires you to go to an area of your own personality that other parts don't require."

That production coincided with the death of his mother, of whom he speaks with great warmth and admiration. It was a performance she never saw. "Of course that had a bearing on my performance," he says. "It must have added extra depth, and my performance was, in a way, a gift to her." But the part itself awakened something new in his acting, he says. "So often acting is about putting on a persona, but Hamlet requires you to strip away, to be in a place which is identical with people in the audience. You become representative of them. That's probably true of Lear as well."

With age comes a different range of possible parts, I say, and he reveals that he is planning a King Lear with his old friend Sam Mendes in the next few years. Mendes is currently rumoured to be in line to direct the next Bond film. Would Beale like a part? "YES!" he bellows, "Of course! Every actor wants to be in Bond. I'd love to be a baddie. I saw Sam just before Christmas and dropped a hint – and he just looked wearily at me."

Film is one area Beale has yet to dominate, though not through want of offers. "If I ever got a choice between a film and a play, the play was always more demanding. The first film offer I got was to play a gay, 35-year-old, Oxbridge graduate, white Anglo-Saxon – or I could do Richard III. Well there's no choice, although I probably played Richard III as a gay, 35-year-old Oxbridge graduate...."

Browsing his CV it's clear he prefers the classical repertory; but then it suits him, with his cut-glass accent and his intellectual engagement with texts. Born in Penang, Malaysia, the eldest of five, his family was solidly English, his father a doctor, mother a teacher. Hard work came early when he won a choral scholarship aged eight, and continued through his time at Clifton College and Cambridge, where he landed a First.

But for all his learning he is not flash, batting questions back rather than showing off when we talk about Chekhov. I wonder if this modesty held him back early on, for despite being at Cambridge at the same time as Stephen Fry, Hugh Laurie and Emma Thompson, he failed to get into the Footlights. "I did go to an audition," he recalls. "It was in front of Hugh Laurie. I can remember it clearly. But I was awful. Really dreadful. So of course I didn't get in."

Now he is virtually as big a name as Fry or Laurie, one of the National's top stars, and now finds people stop him in the street. In the rare moments when he's not working he indulges his passion for books, boxing, crosswords and choral music, on which he is something of an expert. With an extravagant taste for taxis and eating out, he is not yet rich, and his only possession is a "tiny" flat in London.

But it's fair to say he is at the top of his game, a position he has arguably occupied for the past 10 years since Hamlet. He has ticked off all the parts a stage actor could ever hope to achieve, and yet there are no signs that he is flagging. "People say you've done Hamlet so what do you do next? That hasn't happened to me. Not yet."

Curriculum vitae

12 January 1961 Born Penang, Malaya, the eldest of five.

1969 Wins choral scholarship to St Paul's Cathedral School.

1974 Attends Clifton College, makes stage debut as Desdemona in Othello.

1979 Goes up to Gonville and Caius College, Cambridge, to read English.

1983 Graduates from Guildhall School of Music and Drama.

1990 Plays the role of Konstantin in Terry Hands' acclaimed production of Chekhov's The Seagull.

1991 First of many collaborations with Sam Mendes.

1997 Stars as Kenneth Widmerpool in BBC adaptation of A Dance to the Music of Time.

2000 Plays Hamlet at the National.

2005 Plays Cassius in Julius Caesar and Macbeth at the Almeida. In December he joins West End musical Spamalot, playing King Arthur.

2008 Makes debut as TV presenter with BBC Four series Sacred Music.

2009 Plays George Smiley in Radio 4's adaptation of all John Le Carre's spy novels.