Interview: Phil Cornwell: You're wrong. His name is not Michael Caine

`Stella Street' is the Surbiton answer to Beverly Hills, boasting residents like Mick Jagger, Michael Caine and Dirk Bogarde. Jasper Rees gets an impression of the street and its caretakers - John Sessions and Phil Cornwell

For the photograph you see attached to this article, Phil Cornwell moved among the West End masses dressed as mid-period Michael Caine. No matter that Caine is now well the wrong side of 60, Cornwell had to fend off an array of mugs who thought he was the genuine article. "People came up to me and said, `You're Michael Caine, aren't you?' I said, `No I'm not'. They said, `Well who are you then?'"

The impressionist who knows the answer to that question has not yet been born. Mimics universally suffer from Peter Sellers Syndrome, in which they can do the police in different voices but can't seem to find their own. From the swelling ranks of the profession, we can extrapolate that the British have never had a deeper identity crisis. Impressionism, as the craft is somewhat artily known, used to be a one-man industry called Mike Yarwood. These days it supports more careers than ever before. It also finds itself attached to a wider variety of genres than just straight stand-up, from the game show format of Radio Four's First Impressions to the satire of Rory Bremner.

Impressionism is now moving into soap opera. Take an act like Cornwell's Caine, move him to a quiet suburban avenue, multiply by ten, and you've got Stella Street, a nightly saga going out this Christmas in bite-size morsels. Caine has adopted as home this quiet corner of Surbiton (impersonated by a sleepy street in Shepherds Bush), along with a glittering array of stars. From the world of film come Jack Nicholson, Joe Pesci, Al Pacino, Dirk Bogarde and, er, Roger Moore. David Bowie has settled here because it reminds him of Beckenham. Mick Jagger and Keith Richards, taking the sensible view that they are too old to rock, now run the corner shop. The only resident who might plausibly live here in real life is Jimmy Hill.

The show sounds like a job creation scheme for impressionists. In fact the residents who aren't played by Cornwell are done by John Sessions. Neither can claim to have dreamed up this festival of mimicry. They were brought together the Comic Strip guru Peter Richardson, who says "I worked with them separately and thought they were both unique, in the sense that they're not just impressionists. They delve into a subterranean life that may be fictional but has a weird truth about it."

They came up with an initial idea for a sketch in which Moore and Bowie spend Christmas alone together. The cast list fanned out from there, incorporating characters "who just happened to be the people we liked doing best," says Cornwell. He wishes he'd added his Robert De Niro, but acknowledges that that would have been a New York hoodlum too far. Ever the populist, Sessions for his part says "it would have been lovely to have stuck in somebody like Terry Hands", although he's already aware that "with all due respect to Dirk Bogarde, all the baseball hat boys of 15 and 16 are not going to know who he is. He is just going to be a very strange hypersensitive man in a white suit". In order to insert the merest hint of realism, they each do one fictional character as well - Cornwell an odd-jobber in a vest called Dean, Sessions a zimmer-framed housekeeper to the stars called Mrs Huggett.

In practically every respect Sessions and Cornwell have nothing in common. Sessions is a writer and actor with a background in public school and academe who tends to work in solitary confinement. Cornwell is a matey native of Southend, made his performance debut on Canvey Island aged 16, and was soon doing stand-up in East End pubs as a filler between the strippers. Mimicry is their common ground, and Jagger the one voice they both have in their locker.

While Sessions's Mick is more naturalistic, Cornwell's is an extraordinary octave-hopping star turn. It's thought that Jagger once heard Cornwell on Steve Wright's programme and remarked warily, "I don't remember doing that interview." "It would have been flat as a pancake if I'd done Mick," says Sessions. "There are impersonations which are very very accurate, and after you've heard them for two minutes they're dull."

Some of the impressions are more persuasive than others. Richards is actually Sessions's weak link; Jimmy Hill is Cornwell's. While Cornwell thrives on the London accents that are close to his own vowel sounds - Caine, Jagger, Bowie - Sessions is more comfortable inhabiting the New York Italian of Pesci and Pacino. He is aware that his own standards of impersonation vary wildly. "I remember ten years ago going to Los Angeles to do the NBC Spitting Image and working with the American impersonators who were so shit hot. There was one woman who did a triologue between Diane Keaton, Jessica Lange and Mia Farrow. You could have turned your back and it was them. When the NBC guy came over to listen to the script we had he told me 90 per cent of mine were crap."

In order not to make it a series of vaguely connected sketches, a plot was threaded loosely through the ten episodes. "That was the worst part for me," says Sessions. "It just took forever. The plots are tenuous and parodic atrocities of a soap: get an ambulance in there, have a heart attack." However, that is the show's only nod to formal narrative. You won't need to watch too attentively to note that in one shot Stella Street is sweltering in full leaf, in the next the actors' breath puffily condenses in the air. Plus, Cornwell's characters have a habit of losing and gaining weight between cutaways.

Filming, on Hi-8 with a single camera, took place in two four-day schedules separated by eight months. The bones of five episodes were shot without a commission for a mere pounds 4,000 last Christmas. "We didn't know what we were doing with it quite," says Cornwell. "The BBC had said they were interested, but that's all they said. But we went ahead and shot it anyway. Rather than present them with a treatment saying `this is what we'd like to do', we actually said `this is what we've done.'"

The second five episodes weren't filmed until August, by which time it was 90 degrees and Cornwell had lost a stone and a half in weight, making his Nicholson less plausible and his Bowie more so. The very short schedule seems mostly to have involved changing costumes. Rarely, in other words, has a television series with such a high-pedigree cast come to the screen in less organised manner or on a lower budget.

Whichever way you look at it, Stella Street is an utterly absurd programme, but that is precisely its charm. "It's the Munsters," says Sessions. "One just simply must acknowledge the ludicrousness of the fact that Al Pacino lives in the street."