Terry Grimley meets Jess Walters, whose third play for Birmingham Rep is a collaboration with reggae legends UB40...

If playwright Jess Walters, author of the forthcoming UB40 musical Promises and Lies, has a strongly developed work ethic, she thinks she may have her father to thank for it.

He is the Birmingham-born sculptor Ian Walters, whose planned over-lifesized statue of Nelson Mandela for Trafalgar Square has recently been at the centre of an acrimonious planning dispute between London Mayor Ken Livingstone and Westminster Council.

An earlier bust of Mandela by Walters has long stood outside the Royal Festival Hall, while other sculptures by him include the figure of Harold Wilson outside Hudders-field railway station and monuments to Arthur Scargill, Tony Benn and Fenner Brockway.

"He did the Nelson Mandela bust when Mandela was still in prison, and stayed with him at his house a couple of years ago," Jess told me when we met at Birmingham Rep.

"He's doing Stephen Hawking today, as we speak. He's in Cambridge, he's got the day with him. Stephen Hawking approached my dad, which is unusual, because my dad usually commissions himself to do everything."

Spending a childhood surrounded by art - her mother is also an artist - did not seem particularly remarkable at the time: "When you're growing up you don't know anything different, you don't really think about it. Seeing my dad working has definitely inspired me.

It's been a hard thing as a daughter because he was always in the studio working, but that set me up, because I can't not work, and if I don't I feel ill. But when I'm working I get such a buzz.

"Recently my dad and I were chatting about this in his kitchen. When I've been writing this or other plays I can stay up till really late at night. You get to a point where you stop thinking and you allow it to happen. That's why there's crazy stuff in my plays, and those are always the things that audiences like."

Jess has had two plays, Terracotta and Louder, staged by the Rep in its studio, The Door. It was probably particularly the latter, for which she went to the extraordinary length of passing herself off as a Year 9 schoolgirl for several weeks to research the story of a group of teenage girls hanging around a rundown estate, which put her in the frame to write Promises and Lies, the Rep's musical collaboration with Brummie reggae stars UB40.

Usually the gestation period of her plays is comparable with that of her father's sculptures (the Mandela statue, now completed in clay but still awaiting casting in bronze, is about a year away from installation), but this one has been unusu-ally rapid.

"I started work on this job in July and here we are now, eight months later, rehearsing it," she says.

How much guidance was she given on what the show was meant to be? "Nothing...all I was told was that it would need to have an interval, and it would have UB40 songs, including two new ones. I said I had to get all their music, and I went to DEP International [the band's Digbeth headquarters] and they gave me every single album and single from their back-catalogue.

"I knew a lot of their stuff but not all of it. I knew some of their early stuff which I really took to when it came out. I listened to them for weeks and weeks, and at the same time I was told they needed a title. I remember once coming up to Birmingham to do some research and seeing posters and thinking Oh my God, I haven't written it. You can't tell anyone...

"The first draft had 26 songs, excluding the new ones. I'd got past the scary part and went for it. And then they said that's far too many, you have to cut it down to 12. So I had to cut out songs, and characters as well. That was the hardest part of the whole process, because there's a domino effect - if you cut a song out, or a character, that affects everything else.

"It was like starting again. It was good, though, because it meant I had to be very hard on myself. I only had three weeks to do it.

I handed that draft in, then there was a five-day workshop with actors. At the end of the week UB40 came in with their management and lots of people from the Rep - about 40 people. I've written four more drafts since then, but it's been easier. Now we're in the fourth week of rehearsal, and it's going really well."

Promises and Lies is a show about modern urban life, seen from the perspective of people at the bottom of the social heap. But despite its origins, it's not specifically a Birmingham show.

"I was told this musical needed to be something that could travel to other places," Jess explains. "It could be put in any city and you would be able to relate to it. It begins on Friday night on a street like Broad Street, and there are people from all walks of life. There are specific things that people from Birmingham would recognise, but someone else might think it's a night in Oxford Street.

"What I'm looking at is that glossy urban modernness. The lead character is homeless, but a person. These people have been let down by their family or the system. It's really dark, very sad, but really funny as well. It's in your face, but it's not trying to shock.

I think everyone would be able to see themselves in it."

* Promises and Lies is at Birmingham Repertory Theatre from Monday until April 15 (Box office: 0121 236 4455).