Last month, Mamma Mia! celebrated its fourth birthday at the West End's Prince Edward Theatre, having so far grossed more than $500 million worldwide. Since opening, the musical has conquered Broadway as well as visiting Toronto and Melbourne, touring the US and preparing upcoming productions in Germany, Holland, Japan and Korea - to become a truly global phenomenon.

But Catherine Johnson - who wrote the show's original book, fashioned neatly around the greatest hits of 1970s supergroup Abba - started her career in rather more local, and low-key, Shepherd's Bush. In 1991, after productions of her plays Rag Doll and Renegades in Johnson's home town at the Bristol Old Vic, she was made writer-in-residence at west London's Bush Theatre, where she penned Boys Mean Business, Dead Sheep and Shang-a-Lang.

Johnson's television writing credits include episodes of Casualty, Byker Grove, Love Hurts, Gold and Linda Green, and screenplays for Rag Doll, Where's Willy and Sin Bin.

Her career accolades to date have included the Bristol Old Vic/HTV Playwriting award and the Thames Television Writer-in-Residence and Best Play awards. Mamma Mia! was also nominated for an Olivier Award for Best New Musical and, in New York, Johnson herself was singled out with a Tony nomination for Best Book of a Musical Book.

This month, Johnson returns to her playwriting roots at the Bush, with the world premiere of her new play Little Baby Nothing, a comedy about teenagers obsessed with sex and Satan.

Date & place of birth
Born 14 October 1957 in Battersford, Suffolk.

Lives now in...
Hotwells, Bristol.

First big break
Oh, I won the Bristol Old Vic/HTV Playwriting Award with my play Rag Doll, so it was performed at the Old Vic.

Career highlights to date
Something that still stands out for me was the party we had after the opening night of Dead Sheep at the Bush. It was 5.00am and the artistic director, Dominic Dromgoole, broke into the flat I was staying in and started bouncing on my bed where I was asleep. He kept saying - "It's a cracker, it's a cracker!" - referring to the Guardian review which he'd just seen. And I always remember lying there in a drunken haze, thinking, it's my first review and it's a good one.

What difference have awards made to your career?
I think they boost your self-esteem. They help you build confidence and make you want to keep doing it. They aren't actually worth that much, although it is something you can show people to recommend your work. The reality is, your play is only as good as the production. I look on any awards as awards for the productions as much as for me.

Favourite actors
That's not fair, I'll pass on that one I think. If it was 'most fanciable', it'd be easy. Really, all of the actors who are in my show at the moment. Oh, and Bill Murray. He's so clever in that he makes his characters funny and real, but he never compromises or plays warmth for the sake of it, unlike Kevin Spacey. I think Spacey plays to make the audience like him.

Favourite playwright
Chris Hannon. He wrote The Baby which I saw at the Bush in the early 1990s. It was fantastic writing, superb acting and just a pure Bush experience - a play about the Roman Empire set in a space the size of my kitchen. It's the best thing I've ever seen.

What play would you most like to have written?
As much I love The Baby, I couldn't do it justice, so I'll choose Jerry Springer - The Opera because I would love to have people laughing like that at something I'd written.

If you were an actor, what role would you most like to play
I think I'd like to play something in one of mine. Maybe the mother in Little Baby Nothing, because it wouldn't stretch my limited acting skills to do that.

What's the best thing you've seen on stage recently?
Well, I'm going to have to go for Jerry Springer - The Opera again. I want to see the Owen McCafferty play, too, Scenes from the Big Picture. I think if I'd seen it I might say that, but I haven't, so I'll stick with Jerry. I saw it two weeks ago and I'm still humming the songs.

What would you advise the government to secure the future of theatre?
More money, it's that simple. And be adventurous.

If you could swap places with someone for a day, who would it be?
My daughter, because she seems to have her life better sorted than I do. No, that's not fair to my son, I won't say that. At the moment, I wouldn't be swapping with anyone. I've got one play in the West End and a new one opening tonight at the Bush - I couldn't be happier.

Favourite books
Anything by PG Woodhouse - say the omnibus, then that gets them all in.

Favourite holiday destinations
Weston-Super-Mare never fails.

Favourite websites
The one I use the most is Sainsburys Direct, but my favourite is It's the best. They send you a newsletter every week with lots of scandalous gossip. It's such a laugh.

What made you want to write plays as opposed to films, TV or novels?
I think it's because my Dad used to take me to the theatre a lot. I love the real-time aspect of stage. Also, when a play is good, it's a tremendous feeling that you don't get from anything else. It's not the same with TV or film. When it came to writing for theatre, I felt at home. I went to the theatre once a fortnight for ten years before I started writing, then, when I did start, I found my voice through other characters. I can't write prose at all - it's awful, so self-conscious. I need to be in character to write. But it's hard to leave them behind, so sometimes I find I'm talking like my character!

What impact did becoming a Bush writer-in-residence have on your work? How important do you think such schemes are for the arts?
It's incredibly important. It taught me my trade and gave me a profile in London, which led to telly work and money. The Bush is a fantastic theatre to work for, so caring to new writing - which is their remit and they do it best. It was also wonderful to feel involved in an organisation. As a writer, you can become very isolated.

How did you come to write the book for Mamma Mia!?
The producer, Judy Kramer, had been looking for someone to write the book for several years. She was working on a TV thing with Terry Johnson at the time, and he recommended me, so it's thanks to him.

Was it difficult turning your hand from plays to a musical?
Yeah, I thought of it like a jigsaw with only half the pieces because, of course, I had all the songs. It was a case of putting it on a table and trying to make it fit. Mamma Mia! was more of a mental exercise where as this (Little Baby Nothing) is from the gut.

How do you feel being back at the Bush?
It feels like coming home. The first day of rehearsals is so exciting. Writing is only half the work on a new play. The other half is being with actors and directors and seeing the piece grow. Coming out of the dress rehearsal, I felt like I'd handed my baby over.

What's your favourite line from Little Baby Nothing?
It sounds awful if I say it and it means nothing out of context, but it's when one character, Craig, talks about his mother, who has motor neurone disease. He says: "She called me a dirty stop-out - well, she mumbled something." It's terrible, but that always makes me laugh.

"Little Baby Nothing" is also the title of Manic Street Preachers song. Why did you choose it?
I've got into a thing of always using song titles, it's my good luck charm. Before Mamma Mia! there was Shang-a-Lang. I wanted to find a song title, and that one seemed to fit. I love music. The best bit for me is finding the music for scene changes. I spend more time on that than I do on the script. God, I hope people won't be leaving the play going "good music, shame about the words!"

How have your personal & family experiences influenced your writing? What else provides you with inspiration?
My sister's given me quite a few ideas. I don't mean I've written about her but she's literally given me ideas. This play grew out of doing Mamma Mia!, which is about a mother and daughter's relationship. I guess I wanted to explore that more fully. I have a son and daughter and thought it was time now to write about parenting. I do try to keep my personal life and writing apart, but ultimately they come together. I listen to people and make up stories about them, or use newspaper articles that only give half the story and I try to fill in the gaps.

What can you tell us about your next play?
I'm developing a TV series about toddler groups - so still doing parenting thing - but that's in development, which could mean it will never happen. I'm getting cynical about TV actually. There's also a film version of Shang-a-Lang on the way. Things are hotting up, but it's been three years in the making so I can't get excited about it. This play took a matter of months to get on. That's why I love theatre. It's so immediate - you can write something and have it on in the same year.

Anything else you want to add?
I do think this is a great play for younger teen audiences. It'll be fantastic if we can get them in to see it.

- Catherine Johnson was talking to Hannah Kennedy

Little Baby Nothing opened at London's Bush on 23 May 2003 (previews from 21 May) and continues until 21 June 2003.