When Bad Girls was axed by ITV last year it bowed off the screen in triumph – an eight-year run of 107 episodes, eight awards, continuing sales all around the world, and still, by today’s standards, getting a very respectable audience of 4.7 million. But as the hour comes round for it to be reborn on the West End stage, I have to remind myself of those scary times when it was first broadcast back in May 1999, to be met with a pelting from most critics and downwardly spiralling ratings that today would lead to a swift mercy killing by the schedulers.

Obviously we knew that we were taking a bit of a risk with Bad Girls. A drama set inside a women’s prison, with its combination of emotion and anarchic humour, and a lesbian love story at its core, it was never going to fit the usual prime-time genres. Luckily, we had a first series of ten episodes, long enough to find our core audience and to turn the show into a cult hit.

When people try to wrestle with the concept of Bad Girls as a musical the same questions always dominate. Do you need to know the TV series? Does it have the same cast as on the telly? Is it serious or is it funny? Well, the short answers to those questions are: no, no and both. Striking the right balance of light and shade in the show is crucial, but the variety of emotional tone is exactly what makes Bad Girls special. And that’s why we felt it was perfect territory for a musical, where comedy, drama and pathos are all heightened even further.

Like the TV series, the musical is set in the fictional HMP Larkhall, with an ensemble of the original core characters from both sides of the bars and the same edgy mix of emotional tone. The marketing will tell you that it’s loads of fun – and it is – but it’s also an indictment of our penal system.

The prison world of Bad Girls gave us a contemporary milieu with a stock of big characters in a classic “us and them” conflict. The rich language of prison slang is fertile territory for new lyrics to refresh the traditional rules of perfect rhyme. We were certain that we could create a musical from this material that could stand alone in its own right and be accessible to those unacquainted with the TV show.

Five years ago, when we first conceived the stage show, new musicals in the West End were pretty thin on the ground. The resurgence of musical comedy in the past few years bolstered our plans, although it’s still rare to find a musical that is original, British and contemporary, never mind feminist.

Our first challenge was deciding which characters and stories to feature. We knew that the essential dynamics included the original two officer/inmate pairings: Wing Governor Helen Stewart’s romantic duel with the rebellious lifer Nikki Wade contrasted with the more sleazy relationship of our two baddies, Principal Officer Jim Fenner and the psycho bitch Shell Dockley. The oppositions of those characters pretty much dictated the outline of the story: we needed the Helen and Nikki love story and at the same time the downfall of Jim Fenner.

In the TV show, Jim had been stabbed in the belly with a broken bottle by Shell, had a psychotic breakdown and was eventually killed with a shard of ice in the neck. In the musical we had the freedom to find a juicy new way to give him his dues that would bring the power battle between him and Helen to the kind of satisfying resolution that we’d had to deny our TV fans, for the usual reasons of actor availability and broadcaster diktat.

But it was never going to be an option to cast the musical “as seen on TV”, so we had to find out if and how we could distil the essence of the characters so that they could be successfully transferred to the stage by other actors who could sing. Obviously in theatre we’re well used to different actors giving different interpretations of a particular role, but in television the two can appear to become inextricably linked.

We further complicated the matter by casting some of our TV actors in different roles from those they played on screen. For instance, Helen Stewart is now played by Laura Rogers, who was previously seen on the inmate side of the bars, and Nicole Faraday, formerly in the part of the porn actress Snowball Merriman, is now playing Shell Dockley.

When we staged a workshop performance at the New Players Theatre in London, with only two of the TV cast playing their original characters – Helen Fraser as Body-bag and Maria Charles as Noreen Biggs – the response of an audience of Bad Girl sfans was overwhelmingly positive. There was just one complaint: that Nikki Wade should have short dark hair . . .

Viewers’ expectations need to be balanced against the more pressing desire to create something fresh and original. Impersonations of other actors’ performances would have been dull, but we did have to consider carefully the extent to which our stage cast should match the look of the TV cast. With characters such as the Two Julies, it was key to the original conception that they were a pair of prostitutes who deliberately styled themselves to try and look alike, even though one was small and the other tall – and we’ve kept to that in the musical.

With Nikki Wade, however, the key thing is that our hero figure and romantic lead has to have a quality about her that we can really believe would turn Helen Stewart’s head and throw her into emotional disarray. She basically has to have an irresistible look and demeanour that any one of us – male, female, straight, gay – will find attractive. And we proved that being a cropped brunette really isn’t an essential part of that recipe.

The character of Yvonne Atkins appeared towards the end of the first TV series and made an immediate impact. Her opening exchange with Sylvia Hollamby is the same in the musical. Sylvia: “You might be famous on the outside, Atkins, but you won’t be in here.” Yvonne: “Wanna bet?”

Yvonne is powerful, charismatic and clever. In the musical, played by the fabulous Sally Dexter, she arrives with a coat stashed like a mini bar and shares out the booze with all her new chums. Of course we do know that in real life it’s unlikely that she’d get through security like that – even with the threat of a visit from her gangster husband Charlie – but this is one of those moments where we do allow ourselves to enjoy the fact that it’s a musical, and the booze puts the women in the mood for Yvonne’s big party number, The A-List.

With its TV incarnation now at an end, Bad Girls: The Musical can establish its own identity and become a standalone show in its own right. And fans of the show will be able to enjoy seeing Helen Fraser fulfil her lifelong ambition to be in a West End musical.

On top of that they’ll also get Jim Fenner and his fantasy chorus-line of dancing prison officers, a death, a riot, a love story, some serious issues and some very serious fun, with an ending that wipes away all memories of Yvonne’s corpse left rotting in the old hanging cell at the end of series five. Just a typical day at HMP Larkhall, then . . .

Fenner’s a goner – and other top Bad Girls moments

Yvonne’s death Evil Jim Fenner traps Yvonne Atkins in the hanging cell beneath Larkhall – she thinks it’s an escape route. She dies horribly of suffocation or starvation or dehydration.

Nikki and Helen reunite The fans’ favourite lesbian coupling of seasons one to three, the wing governor (Helen) and prisoner (Nikki), finally get together after Nikki’s release. The nation cheers.

Bodybag’s trip Sylvia dances the night away (unwittingly) on E. Also, inmate Shell Dockley sets fire to Bodybag’s (alive) husband while he is incarcerated in a coffin.

Fenner’s death Larkhall’s much-hated officer is stabbed to death with a sharpened blade of ice – yes, really – by Julie J.

“It’s a miracle” Kate O’Mara leaps from her wheelchair, cured suddenly of her “paralysis”.

Bad Girls previews at the Garrick Theatre from August 16 and opens on September 12. Box office: 0870 0400083/0870 8901104

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