There are two things the actor Alec Newman swore he'd never do: appear in a Restoration comedy and do a commercial musical. This year, however, the Glasgow-born actor, whose early stage highlights included a turn opposite Cate Blanchett in David Hare's play Plenty, has just returned from Hollywood to appear onstage for the first time in five years.

The first show he appeared in was a revival of The Soldier's Fortune, a Restoration comedy. And now he is previewing in the stage adaptation of Susan Seidelman's 1985 movie Desperately Seeking Susan. (The film was notable for featuring one of Madonna's earliest ventures on to celluloid, following Seidelman's direction of the Into the Groove video.) Newman plays Dez, the male lead originally portrayed by Aidan Quinn in this merry-go-round of mistaken identity among New York's singles set.

The new version not only hops aboard the gravy train of putting hit movies onstage; by framing its narrative with a soundtrack of hit singles by Blondie, it capitalises on the box office that jukebox musicals such as Mamma Mia have become.

"It actually feels like a big movie," Newman muses, "because there are all these MGM people shuffling around wanting to make sure their rights aren't being infringed upon. But I think most of the tickets will be sold on the strength of Blondie, to be honest. It's a shamelessly commercial exercise - and shamelessly fun. I have friends about to play in Othello and Michelangelo, and here I am playing a guy played in a film by Aidan Quinn, and that just makes me giggle.

"Believe it or not, I was attracted to it by the darker, sadder elements of the character. He's a loser, but also a romantic, and his journey is about learning how to make a decision for himself. All that has been beaten out of me in rehearsals. Be louder! Be faster! Be funnier! It has to be blurted out - and that's really irritating, to be honest. There's nothing subtle about it. But that's the genre we're working in, and you have to respect that.

"Shows like this exist because people want to know exactly what they're going to get for £55. I'm very sad there's not more straight drama in the West End, and this show is one of the assassins of that. But if I've paid 55 quid, I want to see something that's going to go off like a bomb."

When first approached to play the part, Newman was still resident in Hollywood, and was forced to audition down the telephone. "Picture this," he says, in the first of a stream of Blondie song-title gags involving hanging on the telephone, in the flesh, etc. "My girlfriend was in one room, the dog was sitting next to me cocking his head and wondering what on earth was going on, and all the while I'm having to sing this song into the receiver with everyone listening on the other side of the world."

Whatever such indignities, Newman's musical credentials are in the blood. His father is Sandy Newman, who began playing in bands as a teenager, including the Chris McClure Section. In 1975 he took over as singer with Marmalade, who'd scored a number one in 1969 with the Paul McCartney-penned Ob-La-Di, Ob-La-Da. In 1976, they made the top ten one last time with Falling Apart at the Seams.

Long before he appeared in the video for McCartney's 1997 single Beautiful Night, Newman junior was growing up listening to the ex-Beatle on cassettes in his dad's car. There's even a Beatle connection in Desperately Seeking Susan - alongside Newman in the cast is the actress Leanne Best, daughter of original Beatles drummer Pete Best, who was famously ousted in favour of Ringo Starr.

It was football rather than music that initially appealed to Newman, though an injury put paid to his ambitions. He turned to acting after his local branch of the Cub Scouts was over-subscribed, and a Friday-night drama club allowed him to discover his inner show-off. A stint at the National Youth Theatre and drama school took him to Edinburgh, where he appeared at the Royal Lyceum in Brian Friel's Translations, and as Tom in Tennessee Williams's The Glass Menagerie.

His appearance opposite Cate Blanchett in Plenty gave him his first whiff of Hollywood. Newman describes his former co-star as "absolutely spellbinding. She was like that just eating a sandwich. I knew at the time I was privileged, but since she's become God's gift to actresses I realise exactly how lucky I was."

On screen, this year has seen Newman get back to his roots in the Edinburgh-shot Reichenbach Falls. "I play a manic-depressive, alcoholic Scotsman," he says of the film, based on an early Ian Rankin short story. "Apart from anything else, it was great being back in Edinburgh. That's where my first job was, and just the smell of the brewery sets me off."

Given how well he got away with an American accent in Hollywood, Newman can see the irony of doing a New York-set musical in London. Beyond Desperately Seeking Susan he's already lined up for Three-Way Split, a Grand Prix-set buddy movie with James McAvoy. If, that is, "we're not too old to play the parts we've been workshopping for two years.

"Age has made me a lot more ambitious than I used to be," he confesses. "I've always had this lack of awareness of time, but now I'm 32. I used to be 25, and tomorrow I'll be 48. I'd hate to be 85 and sitting there wishing I'd said yes to something I didn't."

  • Desperately Seeking Susan is at the Novello Theatre, London, until April 19.