The Alchemist: The dream team

They are both at the pinnacle of the acting profession. Laden with Olivier and Evening Standard awards, they have had oddly similar careers. They both made their names in foppish parts, have both worked extensively with the Royal Shakespeare Company and the National Theatre, and are now associate directors of the latter. Each has starred in a major television series and in a high-profile stage musical. Trained at university and at drama school, they speak verse with extraordinary wit, speed, intelligence and fervour.

Yet it has taken Simon Russell Beale and Alex Jennings more than 20 years to coincide on stage in a play. They do so now in Nick Hytner's Olivier production of Ben Jonson's brilliant farcical satire, The Alchemist. They portray a couple of con-men who operate from a house in Blackfriars, where they exploit their victims' desperate gullibility in a variety of scams.

I met up with Russell Beale and Jennings during a lunch-break from rehearsal. It soon becomes clear that, as a double-act created in heaven but long delayed on earth, they are busily making up for lost time. Like all great theatrical duos, they present a potentially combustible contrast of physique and temperament coupled with a telepathic compatibility. Ideas tumble from the squat, meaty Beale, while the tall, debonair Jennings offers drolly paced, self-deprecating interventions.

They both played Hamlet when, as Jennings wryly remarks, they were "not in the first flush of youth" - indeed when they were pushing 40. "Of all parts, that's the one that's going to identify the type of actor you are", Russell Beale argues. If so, this suggests that Jennings is a dazzling chameleon (his Hamlet was a scathingly playful shape-shifter) while Russell Beale is an actor whose performances are like the latest instalments in a complex spiritual autobiography (his Hamlet was movingly informed by the recent death of his mother). "We've had a gag during rehearsals," says Jennings, "that my career has been based entirely on seeing Those Magnificent Men in Their Flying Machines at an impressionable age, whereas with Simon, [he adopts a self-mocking soppy-pious tone] 'I always go for the truth'"

"We both have moments in the other camp", says Russell Beale - for example, he's given several vertiginously high-definition performances (such as his unforgettable diseased-fop take on Thersites in Troilus and Cressida) and Jennings has produced portrayals that seem to draw on deep personal feeling (such as his brilliant study of Leontes as a dangerous combination of man and arrested boy in Nick Hytner's version of The Winter's Tale). But they agree that this distinction is broadly true.

Performing Ben Jonson puts a premium on the chameleonic style of acting. "They don't have a hinterland, these characters" says Russell Beale. "There isn't that sense of a huge landscape behind them of love and loss". He plays Face, who met Jennings's higher-born Subtle when both were on skid row. He subsequently got a job as a butler. While the master is away, he installs Subtle (who poses as an alchemist) and scouts round for likely victims. "There's a lot of tension between them based on class and education," reports Russell Beale, talking about the dynamics of the comic double-act. They have to play an assortment of invented selves, tailored to the particular desires of each client.

Hytner's production is in modern dress and finds, says Jennings, "absolutely contemporary equivalents for the yearnings of the dupes". Drugger, the tobacconist who superstitiously seeks advice on how best to arrange his shelves, is introduced to the faddism of feng shui. Kastril, the would-be angry young man who wants to be a champion quarreller, is taught the art of the rap-battle. "Here we are, two little middle-class white boys and we've watched all these videos about rap-battles," laughs Russell Beale. "Yes, you're about to get my nearly-50-year-old Eminem," threatens Jennings. There are dizzying changes of tack. "We've played around with the idea of getting muddled and suddenly swapping performances", he explains.

Nowadays, I suggest, the clients would all long to be made famous. "Yes, fame is the modern drug of choice," agrees Russell Beale. And fame (in the sense of becoming a household name) is something that has managed to elude these two superb actors. "Well, we've been slogging away in the theatre, I suppose," says Jennings. After Stuff Happens (the David Hare drama in which he portrayed George W Bush), Jennings decided to have a break from the stage and get in front of a camera again. He has played Diaghilev in a television drama about The Rite of Spring, and he is Prince Charles to Helen Mirren's monarch in the forthcoming The Queen.

But both he and Russell Beale give the impression that film means much less to them than the night-after-night pressure of performing live on stage. "You do it. You film it. You distance it. And it seems to have nothing to do with you when it goes out," says Russell Beale, who offers an example. He starred as the creepy Widmerpool in the television adaptation of Anthony Powell's Dance to the Music of Time, and had to age from schoolboy to septuagenarian. "Widmerpool was famous for being odd at school and nobody knew quite what was wrong with him," he says. "I read a review in The Independent - it was terribly funny: 'What was it that was so odd about the schoolboy Widmerpool? Was it the cut of his raincoat, or was it his horrible mother? Or was it the fact that he was 37 years old?'. If that had been written about me in a play that I was doing, I'd have been devastated, but because the series was made six months before, I howled with laughter".

Next year, he will take over from Tim Curry in the Monty Python musical, Spamalot, as he did (to much acclaim) in New York. Jennings has no settled plans ("You haven't been offered anything, have you?", Russell Beale teases him.) But after finally managing to get together in a play after all those years of mooted projects that turned into near misses, they say that it's likely that they will collaborate again soon. "I absolutely hope that we do," declares Jennings.