Sam West: 'My parents are coming and I'm expecting to get notes'

He may be an established British actor, but as Sam West makes his directorial debut, will Mum and Dad prove to be his harshest critics?

Sam West drives some theatre fans to distraction. In Stratford recently, a besotted drama student admitted he'd come to see the actor play Hamlet six times. But if you haven't seen West – who's starred in 17 films to date, including Iris, Notting Hill, Pandaemonium and Howard's End – chances are you've heard him, since he's the voice of choice for any TV documentary after a bit of honeyed gravitas and lends his mercurial accents to many a radio drama.

But now West, at 36, has recast himself as a director. For a warm-up, he staged a shoestring-budget Hamlet for the unofficial RSC fringe. Having tackled Christopher Fry's The Lady's Not For Burning in Chichester's Minerva studio, he progresses this month to his first mainhouse production: Les Liaisons Dangereuses at Bristol Old Vic. It's an exciting time for the theatre. Its new artistic directors, David Farr and Simon Reade (formerly the RSC's literary manager) plan to put the venue back on the map, but is Christopher Hampton's drama about French aristocrats' sexual intrigues just before the Revolution the right place to begin?

West is softly spoken as he explains that he was "asked to raise the curtain with this play because it marries the historic and the modern". The Vic, one should explain, is a beautiful 18th-century auditorium in a 20th-century shell. "Since the Thatcher era when Hampton wrote the script," he adds, "the 'greed is good' philosophy hasn't entirely gone away. We need to put this play on to see what we might become if we're not careful, and it should be a really vigorous row between hedonism and responsibility." West is politically engaged, supporting the Socialist Alliance and being an active union member. "I write a lot of cross letters," he says.

But he's not planning to turn the play into a piece of agitprop. "Les Liaisons... is also very funny and sexy," he points out, "and luckily I have a very funny and pretty cast." Dervla Kirwan (from Ballykissangel) and Kylie's ex, Rupert Penry-Jones, play Merteuil and Valmont.

This play aside though, why has West stepped across the footlights? "It is nice to take ultimate responsibility," he says. He was also encouraged by director Steven Pimlott (for whom he played Hamlet).

"Directing," West remarks "uses the other half of your brain. It's objective while acting is subjective. I'm more analytical – and not subjective enough sometimes." Perhaps the result of his academic Oxford University days or his scientific bent at school when he had a mind to become an astrophysicist.

Has he, one wonders, got bored of acting or been frustrated by casting agents? He has bewailed the industry's "fashion for foetuses" and – probably because of his bruised choirboy looks – he acknowledges he's been typecast as a damaged toff. "But no, I didn't get bored," he says. "I'd have played Hamlet for another year."

Still, what do you do then? Wait for Lear? "In taking up directing," West says, "I side-stepped that question." That said, he's keen to point out he's not signed-off as an actor. He's been making a BBC series, Cambridge Spies, which comes out in April. "I'm Blunt, Rupert is Maclean, Tom Hollander is Burgess and Toby Stephens is Philby, thank you very much! And last Friday at 3am, I was playing Frankenstein for a new Universal movie – on top of a burning windmill in Prague in the arms of the monster who was shouting 'Father! Who am I?'" As for classical theatre, he says: "I'd love to play Iago and, yes, Lear, since you ask – in about two years. My dad first played that part at 37." Tim West's current Lear is, by a curious coincidence, opening at London's Old Vic the same night as Les Liaisons...

West's theatrical parentage – his mother is Prunella Scales – is well-trodden ground. But the "family business" actually goes back several generations. Sam fondly recalls seeing his paternal grandfather Harry Lockwood, aged 75, at Drury Lane in Billy Liar. Lockwood's father-in-law, C Carlton Crowe, was Robert Donat's batman in the original Goodbye Mr Chips, and Sam's grandmother, Catherine Scales, also trod the boards.

His parents are coming to a preview, "and I'm expecting to get notes," he says with a grin. He's acted with them on many occasions, but will he direct Mum and Dad one day? "I think that might be too smug for words, don't you?" Meanwhile, ENO have called to discuss a possible Così for them at the Barbican. West is certainly expanding the family firm's output. "I'd love to direct for the screen as well. So if someone wanted to give me a go..." he hints, as he races back to rehearsals.

'Les Liaisons Dangereuses': Bristol Old Vic (0117 987 7877), to 5 April