Cad files: Sam West turns supervillain in a new play about the collapse of energy titan Enron

What must it be like to have achieved all one's ambitions? Sam West has just turned 43 and discovered he has done everything he thought he had wanted: "I've played Hamlet, been in Doctor Who and read the shipping forecast. I'm having to draw up a new list." Luckily, there is plenty he still wants to do (including the shipping forecast on Radio 4 proper, as his first go was only in a play).

When we meet, he is midway through rehearsals for his latest project, the première of Enron, by young playwright Lucy Prebble, about the collapse of the US energy giant. "Apart from being a brilliant play, the timing couldn't have been better," says West. "It was commissioned two years ago, just before the banking collapse and it comes out just when people are asking how the hell it happened."

West plays the part of Jeffrey Skilling, the CEO of Enron (the US corporation that went bankrupt in 2001 as the result of an accounting fraud) who is presently three years into a 24-year jail sentence. It's quite a departure from West's previous roles, which have included Ted Heath, Anthony Blunt and a number of other English eccentrics.

Skilling is the Machiavellian charmer from Illinois who had never run a company before Enron but discovered that as long as the share price stayed high, investors would continue to pump in money. West is fascinated by Skilling, even though their politics could not be more different. West is a former member of the Socialist Alliance, Skilling a rampant free-marketer. Yet when he talks about Skilling, West could almost be talking about himself: "What drives him? A belief in ideas. A belief in the purity of the idea. A belief in brilliance."

West has a strong moral instinct and a keen sense of injustice. He is spitting at the news that Stephen Hester, Sir Fred Goodwin's replacement at RBS, is to get a £10m package, £6.4m of which is conditional on the share price rising. "Have they learnt nothing?" he rages. "It's not socialism, just common sense to know not to reward irresponsibility at a time when banks are meant to be less risky. You can't give someone £6.4m if they hit a certain share price at the same time as letting 3,000 people go."

West has what the Prime Minister would call strong "values". It's refreshing to meet an actor more interested in politics than his own IMDB listing – though West's is impressive. His big break came when he got the part of Leonard Bast in Howards End aged 26, and he was soon in demand for period dramas including Persuasion, Jane Eyre and Carrington. "They were great fun," he says, "although one can be tarred by the linen brush."

It was that fear of becoming too used to playing parts in petticoats that prompted Helena Bonham Carter to give up Merchant Ivory dramas and go to the US, where she wowed her critics with her American accent. "People don't need any encouragement to put you in a box," admits West. "And I have been mostly lords and princes. But I would be foolish to turn my back on Merchant Ivory. You have an idea as an actor as to what you think you can play, but it's much more important to know what other people think you can play. If you get a chance to play a very different animal, in terms of their background and their country, it's delightful."

West hails from theatre royalty – his father is Timothy West, his mother Prunella Scales – but he doesn't believe he was ever given a part because of who they were. "That would be absurd. The only difficulty is that you don't quite decide to become an actor. I've just gone into the family business." Growing up with famous parents was never a problem, as he didn't know any different. "There was a time when they were big names, when mum was in Fawlty Towers and dad was in Edward VII. Occasionally I would be asked at school to get an autograph, but there was no reflective glory."

Unlike some power families, the Wests were not competitive, but rather operated with a spirit of collaboration, reading each other's reviews and seeing each other's performances. "I remember getting a review at Oxford that said I was OK but I didn't have the presence of my famous mother and father. I was playing Florizel in The Winter's Tale and my father said, 'I think that's very unfair. I mean, I would be hopeless as Florizel and Ma would be even worse.'" Rehearsing Enron has made West grateful to be an actor. "Acting is, unusually, a collaborative medium, not a competition. And I'm now involved in making a play about a company that is not a company, but a competition. As a group, we are trying to get on as well as possible so that on stage we can beat the shit out of each other."

Apart from a bit of waitering, West has never had a job beyond actor or director. He says the real stars, though, are the writers; West has never attempted to write for stage or screen himself, although he reveals he is supposed to be writing a book about how to approach a variety of roles. "It's going rather slowly. Writing isn't really my thing," he admits.

West is consistently modest about his achievements. The first play he ever directed, Hamlet at the Edinburgh Fringe, so impressed the Almeida's artistic director Michael Attenborough that he gave West a job at the theatre seven years later. His enthusiasm for regional theatre led him to take on the post of artistic director at the Crucible complex in Sheffield in 2005, although he stayed for only two terms after a disagreement with the managers – he wanted to put on plays while the theatre was closed for refurbishment, they didn't. He also found the distribution of funds frustrating. "It's no secret that marketing departments in regional theatres have grown massively while the number of actors in work has reduced," he says. "There is a fight to be had for the soul of regional theatre in this country. I suspect that the culture of over-management has reached the stage where artists are seen as slightly tiresome people who want to spend money on things that don't make profits. And if you use a monetary model, a regional theatre can be seen as very unproductive. I suspect we should be fighting for our theatres as we do our car factories."

The experience has not put him off, though. He would like to run a theatre again one day, although "because it becomes your baby", he plans to start a family first. He lives in Islington with his partner, the playwright Laura Wade, and hopes to have children soon. Achieving one ambition leads to the next, it seems. In fact, his list has never been longer, but does he really mean it when he says he wants to be James Bond? "Everybody says they want to do Hamlet, and nobody ever jokes about wanting to be Bond. But it's the part everyone secretly wants to play. I would." With his experience of playing toffs, frauds and serial killers, he'd be perfect for the part.

'Enron' runs from Saturday to 29 August at Chichester Festival Theatre (01243 781 312, www.cft.org.uk)

Tips for aspiring actors by Sam West

Try to stay solvent so you don't have to do rubbish. You might be tempted to take the first well-paid part on TV, but it might prove to be more damaging than beneficial.

Try to be happy for your colleagues' success. Acting is a collaborative art. In rehearsals it is vital to work as a team.

Remember that the writers are the true stars. Actors take a lot of the credit, but the playwright and screenwriters are the true creative forces. Without them, we wouldn't be able to exist.

You may have an idea as to the parts you think you can play, but it's much more important to know what other people think you can play. If you get a chance to play a very different sort of part to one you would normally take, then do it.