Stephen Churchett spent many years playing bit-parts in TV series like `The Bill' and `EastEnders'. But West End stardom always eluded him - until he wrote his first play.

As his second, `Heritage', is about to open in Hampstead, he talks to Jasper Rees about his new-found success as a playwright.

At what point does an actor who starts to write plays begin describing himself as a playwright? This is the first question I ask Stephen Churchett, who has been an actor for years without ever quite getting his name in lights. Then he goes and writes one play and, four days shy of his 50th birthday, he's opening in the West End, a theatrical inner sanctum he very rarely penetrated as a mere spouter of other people's words. Now he has a second play, Heritage, opening at the Hampstead Theatre next week. "I can say I'm an actor who's written two plays," he says. But he reconsiders. "I am an actor and a playwright."

You might recognise the appealingly round face and the naked pate from this supporting role or that peripheral part in various long-running light entertainments. Then again, you might not. Jack Druggett in The Brittas Empire? Joseph Wint in The House of Eliott? He pops up in EastEnders as the Mitchell brothers' dodgy solicitor, but only now and then. "I haven't done an episode of EastEnders for about a year," he says, and calculates that he may have been in no more than 12 episodes overall. "I don't watch but my mother does. She says, `Oh, they were talking about you on the phone the other day.' That must mean they're going to have me back. But maybe it's cheaper just to have them talking to me on the phone." When he had more hair, he played a patient in a day centre for people with learning difficulties in Bleak Moments, the first ever Mike Leigh film. You'll see him next as a senior hospital manager in McCallum.

You get the picture: nearly 30 years an actor, and stardom in all probability no longer lurking round the corner. Then, two years ago, Churchett decided not only to start on a play, which he had managed often enough, but also to finish it, which he hadn't. Previously on his script-writing CV there was one episode of The Bill (in which, as an actor, he has also appeared in various guises). So his first play, Tom and Clem, emerged from more or less untilled soil. It imagined an ideological encounter at the Potsdam conference in 1945 between the cavalier and roundhead wings of the post- war Labour party - the radical, extravagantly homosexual MP, Tom Driberg, and the pragmatic, stolid Prime Minister, Clement Attlee.

"It was the first thing I'd written that I was really rather pleased with. I finished and I actually thought, this has got potential." He pitched it to the agent of fellow actor-turned-playwright Kevin Elyot while they were filming a pub scene for the television version of My Night with Reg. Within a week or two, Churchett was sitting across the desk from Michael Codron, the high-brow impresario who puts the likes of Tom Stoppard on in the West End. "It was the most important audition of my life, except I was the only person up for the part. Michael would hate me to say this but he can be slightly frightening. There are silences. I noticed an ashtray and I said, `Would you mind if I smoke?' He said, `Stephen, let's have a cigar.' I thought, this is silly: am I in a play or am I talking about one? I hate cigars." But, mindful that it might get his play mounted, he smoked one anyway.

With Michael Gambon and Alec MacCowan starring, and Richard Wilson directing, Churchett's first ever play opened at the Aldwych after a fortnight in Guildford. For West End, read deep end. Debut plays by complete unknowns with stellar casts may well have sprinted down the same fast track before, but can you think of one?

For Heritage, the procedure has been more conventional. Hampstead, unlike the Aldwych, is a traditional nursery of new writing, and only after a seven-week run there, followed by a six-week national tour, might Churchett's second play follow his first into the West End. "Sufficient unto the day..." says its author. "It's not impossible, I suppose, but one wouldn't want to count any chickens."

For his latest play, written before Tom and Clem had been produced, Churchett has set himself the task of inventing his entire cast of characters. The setting is real enough, though: a London hospital where crusty veterans in smart scarlet livery reside in semi-military retirement. "Although it's never stated, it is very obviously the Royal Hospital Chelsea, where the Chelsea Pensioners live," says Churchett. Harry is one such OAP, bridling against a proposed takeover of the institution that will see it gradually converted, as the old boys drop off, into a museum and conference centre. Harry (played by George Cole) keeps his curmudgeonly chin up with the help of visits from his son George, daughter May and grandson Rupert. They have their own grievances too - George's boyfriend has just died; May's husband is married to his job, which just so happens to involve overseeing the conversion of the hospital; and Rupert can't see the point of his university course - and it's clear that these visits address their own needs as well as Harry's.

"The play is called Heritage because I think it's a desperately undervalued word. We just associate it now with theme parks. One of the reasons that made me set a play in an institution like this is that I went to the Royal Naval College at Greenwich a couple of years ago for a carol service. This may be an apocryphal story but I was told by a couple of people who were singing in the choir that the then heritage secretary Virginia Bottomley stood in the Wren chapel and said, `This would make a marvellous lecture theatre.'"

In its way, Tom and Clem made a marvellous lecture theatre too. The chief criticism was that it failed to find a harmony between the drama of ideological head-bashing and the personal relationship between its two protagonists. Heritage is less nakedly concerned with polemic and, although more modest in thematic scope, feels all the more entire for it, on the page at least. Churchett is currently in the very early stages of writing a third play - "about the retreat from rationalism. Why, after hundreds of years of people working out how the world does work, and being imprisoned for saying that the solar system works in this way, suddenly we seem to be going back to crystals and all that?"

The first draft should be finished by the spring. Or maybe not. "If I suddenly get offered a lot of acting work, it means I'll have less time to do it."

`Heritage' starts previewing on Thursday at the Hampstead Theatre, London NW3 (booking: 0171-722 9301). To 17 Jan 1998