Lucy Prebble - playing with fire

'I can only write about things that frighten me,' says Lucy Prebble briskly, eating a chip. 'I've no idea why. It has to feel slightly thrilling, so I'm completely filled with selfdoubt and yet compelled to do it. It's like having an affair: "This is so wrong, but it could be so great!" '

A bit twisted, perhaps, but her high-adrenaline approach to playwriting produced Enron, the audacious all-singing, all-dancing theatrical account of the collapse of the American energy giant. It delighted critics, sold out all 21,800 seats of its run at the Royal Court and has just reopened in the West End at the Noel Coward Theatre, with Broadway and film versions forthcoming. In short, it has been a stonking success, something Prebble is determined to enjoy, as she tells me over moules frites at J Sheekey. 'I'm out every night with the cast - there's a wonderful celebratory mood.'

Diminutive, feminine and only 28, she recently discovered what she laughingly calls 'the double take'. 'When I'm introduced, people say,' -adopts bored tone - ' "Oh, hi" and then when they know what I wrote, they turn round and say,' - adopts voice of gushing excitement - ' "Oh, hi!" ' The other day, she received a card of congratulation from Tom Stoppard. 'I jumped up and down when I got it. He didn't need to do that. It was classy behaviour.' But there are also anxieties. The former head of Enron, Jeffrey Skilling, has not yet been in touch. 'When I open my post I sometimes think, "Please don't let this be the letter from Skilling's lawyers..." ' Then again, as she says, it's relatively hard to defame someone who's in prison - and besides, the play is far from a straightforward condemnation. It shows how fun, how seductive it is to be inside an economic bubble. Celestial singing represents the 'empty, beautiful purity' of commodities trading inside Jeffrey Skilling's head, and there are tender scenes between him and his baby daughter (who is, appropriately, blowing bubbles).

'You can write these men off in a sentence but it takes a whole play to understand them,' says Prebble, who has made a career out of understanding people widely considered to be beyond the pale. At 22, fresh out of Sheffield University, she wrote her first professional play, The Sugar Syndrome, a sympathetic, funny portrayal of a paedophile. On the back of its success she got the job of adapting Belle de Jour, the phenomenally popular diary of a real-life prostitute, for television. Originally commissioned to write hour-long episodes for Channel 4, she had hopes of making it into a substantial piece of work, but it all ended rather differently: as 35-minute bites of titillation on ITV2, advertised with Billie Piper's bottom all over the billboards.

'It was a show that didn't achieve the potential I wanted for it,' she says through gritted teeth. 'I think it could have been a lot better. It was marketed in a very...' she grimaces with the effort of having to be tactful, 'particular way, which was problematic-for me. I don't think that's a secret from anyone involved. Billie Piper is an incredibly talented actress, I think she's wonderful and I'd like to think of her as a friend. But I don't work on that show any more.' Secret Diary of a Call Girl didn't even make her a great deal of money, but it did buy her the time to work on Enron, a play that went through 'at least' 17 drafts until it achieved its whip-cracking pace and gleaming polish. 'I always wanted to write about business, and this was the daddy of all financial collapses,' she says. Perhaps there's a slightly Freudian ring to those words.

Her father, now retired, was the CEO of a software company, and she grew up in the comfortable commuter-belt town of Haslemere, Surrey, with a 'vague concept' of what her father did for a living. 'Probably like many middle-class children, it was just "Dad's at work, Dad's away on business" and then you get to the age of 17 and someone says, "What does your dad do?" And you say, "I dunno, I should really find out." '

She researched Enron in forensic detail. While 'weeping over my tenth book on credit default swaps', what kept her going was annoyance at the 'deliberate obfuscation' of big business, as well as the sense that this was a forbidden world. 'When I was younger, I was always trying to get into places I wasn't allowed,' she recalls. 'I was obsessed with getting into pubs for over-18s.' Her instinct for drama has always been strong, too. 'I was quite secretive as a child, the sort of kid who's a compulsive liar, not as a teenager but before that, at primary school. I was the kid who comes in and says, "My dad invented shoes." Of course it makes total sense now that I became a writer.' Did it get her into trouble? 'Yeah, massively. When I read that Jeffrey Skilling used to wake up at four in the morning and worry about the snowball of deceit he'd created, I had a very vivid flashback to waking up when I was about seven, worrying desperately about all these lies I'd told to impress my friends.'

As a pupil at Guildford High - 'a very academic school, and highly pressured' - she was told she could do anything she wanted, but there was an expectation that this would probably be law or politics or business. Her elder brother and sister both work for the management consultancy firm Accenture. The Arthur Andersen 'android' who appears as a gabbling ventriloquist's dummy on stage in Enron suddenly seems a little close to home. The show's daring vaudevillian troupes - Lehman Brothers is represented as conjoined twins, and traders assault California's energy grid while waving lightsabers - clearly still excite Prebble, who hopes to include them in the planned Sony film adaptation of the play, which she envisages as being 'full of illusion, like The Wizard of Oz'. It's all a hair's breadth away from being utterly mad and inappropriate - a thrill-seeking writer's ultimate adrenaline rush. 'Yes, it's about high finance and, yes, it has line-dancing in it - is that so wrong?' Taking the show to Broadway will add another layer of audacity. 'I don't want it to come across as finger-wagging, as Brits going over and telling them what's wrong with their country,' says Prebble, momentarily concerned, before resuming her usual pert reasoning. 'But then, I don't see it as condemnatory anyway. I don't think all Americans are corporate criminals. Only some of them...'

Prebble is as sharp as a pin, and has an indefatigable work ethic. She goes to every rehearsal and, by night, rewrites the script to suit the actors. For all the show's success, she's still doing extra research. The other day, she went to talk to an American investment banker who once worked for Enron. After the interview ended, he asked if she needed any more money to bring the show to Broadway: even her subjects end up as backers. 'He hadn't read the play, and he didn't know me from Adam. He just thought, "You're all right, kid; have some money." I love that American attitude.'

She once worked at the National Theatre as Nicholas Hytner's assistant, 'secretly reading all the scripts that crossed his desk'. Still, she hasn't been to see David Hare's The Power of Yes about the credit crunch. 'I've spent three years of my life immersed in the financial world. I think I'd rather just stay at home and watch a box set, to be honest.'