Shows based on movies or on pop groups’ back catalogues have become mainstays of the theatrical economy. So the latest musical to open in the West End has the whiff of boardroom cynicism. What happens when you randomly select a famous film and an iconic songbook, yoke them together and shove them out in front of the foot-lights? You get Desperately Seeking Susan, a 1985 film starring a chubby-cheeked Madonna, but fea-turing the greatest hits of Blondie.

In fact, the idea has the humblest of origins, and was anything but cynical in inspiration. Four years ago, two men sat in a Man-hattan bar lamenting the lack of Broadway shows they still wished to see. They idly wondered which acts might benefit from the juke-box treatment.

“Blondie was the first band we thought of,” says Peter Marino, a dancer who had risen no higher up the theatrical ladder than banging dustbin lids in Stomp. “We realised that in a lot of their songs, the characters have a strong need, which is really important in musicals. So, much of their music is open to interpretation.”

Would the musical tell the story of Blondie, in the style of the long-running Buddy and Broadway’s ill-fated Lennon? “No. Their story is interesting, but, thankfully, not tragic enough. Nobody dies. So then we started talking about basing it on a popular film. I honestly can say, at the same time, we thought of Desperately Seeking Susan.”

For New Yorkers who came of age in the 1980s, the film is a snap-shot of the era’s bohemian dance-club chic, more so than yuppies-go-underground movies from the period, such as Something Wild or After Hours. “It was the movie that made me want to move from Long Island to New York,” Marino says. Still, that ought to be have been that. Securing the stage rights to one major property is hard enough, but two?

They reconvened a few days later, with the film and a Blondie compilation, and began looking for coalescence. The opening sequence establishes the disparity between the lives of the two heroines – Roberta, a romantically unfulfilled suburban New Jersey housewife, and Susan, a sassy city girl who communicates with her long-distance boyfriend via the personals, while sleeping with (and stealing from) anyone who’ll put her up. When Roberta assumes Susan’s identity, she is unwittingly entangled in the chase for some priceless ancient Egyptian earrings.

“The first song on the CD was Dreaming, and the opening shot is Roberta getting her hair done, hoping she’s going to find this ad for Susan. I thought, ‘Okay, that’s a good sign.’ The next scene is Susan in the hotel room, just getting done with her trick, so we thought, Call Me. My friend is not a writer, he’s got a regular job. He said, ‘Go ahead, have fun with it.’ So I did.”

Marino spent the next nine months absorbing Blondie’s music, tracking down the first draft of the script and constructing a treatment. His big surgical intervention was to wrench the setting back from the mid1980s to 1979. “I just didn’t think Blondie’s music really supported the glossy world of 1985. The show is about the collision of the suburbs and the pregentrification Lower East Side. Kids who were dressing up and teasing their hair and wearing mascara in 1985 were from the suburbs. But in 1979, punks lived in the city. To have a collision of two worlds, they had to be very different.”

He presented the resulting document to the producer of Stomp, whom he’d met once, and they were soon pitching to Debbie Harry. “Debbie said, ‘I read the treatment, and I’m all for it.’ That was it.”

Doors miraculously swung open at MGM, which owned the stage rights. “Both parties told us they’d been approached at least five times to turn either the movie or the music into a musical,but neither of them had liked what was being proposed.”

The decision was taken to create the show in this country, which embraced Blondie earlier than the band’s native New York. (We also have a higher tolerance for juke-box musicals.) Angus Jackson was hired as a director to steer the production through three workshops and into the West End. To him fell the task of achieving something no director has previously attempted: simultaneously to translate the staccato grammar of film into theatrical language while seamlessly crowbarring a much loved songbook into the tale.

In playing what Jackson calls “the game of luring the audience to a place where they’re suddenly delighted by the appearance of a song that is both inevitable and surprising”, he is helped by a tidy coincidence. Roberta’s surname happens to be Glass, so, when she discovers her husband’s infidelity, she can sing about her broken Heart of Glass with impunity. “Will people be surprised by that? Will it be inevitable? It’s certainly very satisfying,” he says.

Does it matter that, presumably like many audience members in their twenties, neither of the show’s rising West End stars knew the film before auditioning? “I’ve stayed away from the film, because I didn’t want to do a version of Madonna,” says Emma Williams. “We’re not trying to put the film on stage. My Susan has a lot more of an influence from Debbie Harry, Shirley Manson and Courtney Love, strong women in rock.”

“I’ve watched the film once,” says Kelly Price, who inherits Roberta from the memorably daffy Rosanna Arquette. “It was a great performance, but you then discard it and build your own bored New Jersey housewife.”

For aficionados, Marino has ensured that the musical will alight on iconic moments from the film. “We want to see Susan blow-drying her armpits in a bathroom at the Port Authority bus station, Roberta circling the ad with lip-stick, Susan sitting in a bathtub pulling a joint out of her boot.” But it’ll be the songs that sell the show. For contractual reasons, some haven’t made the cut. Denis wasn’t written by Harry and Chris Stein; X-Offender and (I’m Always Touched by Your) Presence, Dear were, but with ex-band member Gary Valentine, whose permission has not been forthcoming. But Harry has written a tailor-made song, Moment of Truth. The remaining numbers from a remarkably eclectic catalogue – Sunday Girl, Atomic, Hanging on the Telephone, Rapture, Picture This, One Way or Another – are part of the collective consciousness.

When Harry attends the West End premiere, it will complete an improbable four-year journey for an idea floated by two bored theatregoers in a bar. Should success take it all the way back to Broadway, does Marino’s drinking companion have a stake?

“I did name one of the characters after him,” he says. “He’s very happy with that.”

Desperately Seeking Susan is previewing at the Novello Theatre, WC2

Editor's choice

• The 100 Best Films of 2009
• The 100 Worst Movies of 2009
• The 100 Best Films of the Decade