Despite a string of succesful TV hits, Kay Mellor has never been so nervous. Tony Greenway talks to her about Fat Friends in Leeds and the national tour.

Kay Mellor is terrified. In just a few weeks, Fat Friends, her first-ever musical, opens at the Leeds Grand Theatre before going on a national tour – and her stomach is performing cartwheels.

It’s funny – funny strange, not funny ha-ha – to see Leeds-born Mellor so rattled. She is, after all, one of the most famous and successful scriptwriters, producers and directors working in British TV, and her name packs an awful lot of power. Her career highlights include creating and writing (or co-writing) Playing the Field (with Lesley Sharp), Band of Gold (with Geraldine James), A Passionate Woman (with Billie Piper), The Chase (with her daughter, Gaynor Faye), The Syndicate (with Timothy Spall), last year’s In the Club (with Hermione Norris) and, of course, Fat Friends, which made a star of James Corden, who is now busy conquering US television as a late-night chat show host. (‘What’s James doing now?’ she jokes. ‘I think he faded into obscurity...’)

So Mellor knows she can write a good TV drama series. She’s done enough of them. But a stage musical? Umm. Not so much. She admits that she didn’t even know what a musical supervisor did before working on this production; but, despite her shredded first-timer nerves, she’s enjoyed every minute of the process. ‘For me it’s wonderment,’ she said. ‘I feel like I’m in a Christmas grotto and every corner I turn there’s something new and exciting. It’s really lovely.’

Fat Friends – the story of a group of women at a slimming club – ran on ITV between 2000 and 2005 and was a big hit, both with the public and Mellor herself, which is why she’s decided to resurrect it as a musical. ‘After Fat Friends finished, I felt it was done,’ she says. ‘ITV wanted another series but I said no and put it in the drawer. For years, though, I’ve wanted to write a musical and loved the characters for two of my shows in particular: Band of Gold and Fat Friends. People stop me in the street and ask me if I’ll write them again, so I thought why don’t I write about characters I still love and know and put them in a situation that lends itself to music? And Fat Friends – which is about accepting who you are – is more relevant today than it was 15 years ago. We’re more obsessed than ever with body size, going to the gym and dieting.’

Mellor has written the Fat Friends book and the lyrics, and she’s also directing the show while composer Nicholas Lloyd Webber (no prizes for guessing who his father is) has written the music. ‘Nick’s dad saw a workshop of it and said to me: “Clearly you have a musical here, my dear”. And I thought that’s all right then! Thank God for that! Then he said: “What you should do now is throw yourself at Jodie Prenger’s feet and ask her to play the part of Kelly.” So I thought let’s do what he says!’

Prenger, whose meteoric stage career was launched nine years ago on Andrew Lloyd Webber’s TV star search show I’d Do Anything, was on board straight away. ‘When she read it, she rang me and said: “Who do I have to sleep with to get this part?’’’ Other cast members include X Factor winner Sam Bailey, Kevin ‘Curly Watts’ Kennedy and, weirdly, the cricketer Andrew ‘Freddie’ Flintoff.

Mellor first met Flintoff when she was looking for a celebrity to play a role in her new BBC drama, Love, Lies & Records, and was as surprised as anyone when she found out that he could act. ‘He came in, I auditioned him and I was blown away,’ she says. ‘He hasn’t got a massive role in Love, Lies & Records, but it’s significant. So that was great - job done.

‘Then I got my Fat Friends head on and was thinking we needed a handsome hunk who could sing. I said out loud: “It’s a shame Freddie Flintoff can’t sing.” And someone said: “He can!” and showed me a YouTube video of him singing an Elvis song. I thought: “Oh my God. Let’s meet him and have a conversation.” Because a four-week run at The Grand and then a massive tour is a much bigger commitment than a week’s filming for a telly series. But we auditioned him properly – and he passed.’

Fat Friends may be Mellor’s first-ever musical, but she’s not a woman who does things by halves. Which begs the question: does she have West End or Broadway ambitions for the show?

‘Well, you know, it would be lovely,’ says Mellor. ‘And every step would be a learning curve for me. But right now I’m hugely excited about appearing in Leeds – and the tour, too.’

Right. So that’s not a ‘no’, then.

‘Well, I know people have their eye on it,’ she says a bit mysteriously.

Really? What kind? ‘All sorts of people,’ she laughs. ‘Television people, film people. But I really want to explore it theatrically, properly. And if I was to be so lucky as to take it into the West End, I would be thrilled to bits to be honest with you. Although I’m as thrilled – if not more thrilled – that it’s happening at the Grand Theatre in Leeds.’

That’s understandable: Leeds is her home town and the place where Fat Friends the TV show was originally set. But then Yorkshire has always inspired her writing. ‘I think it’s the people and the place,’ she says. ‘Both are amazing. I live two minutes from the town and five minutes from the country. Leeds in particular is a wonderful city. I’ve watched it grow and become a centre for commerce and the arts and I’m incredibly proud of it and my Yorkshire roots.

‘When people visit I tell them: “You must go to Brontë country, you must go to Sheffield, you must to Saltaire” because it’s all steeped in history and it’s just beautiful. I’m working here now with a couple of actresses on a show called Girlfriends who are in awe of the place.’

Yes, talk about ‘busy’. Girlfriends is a new six-part drama starring Zoë Wanamaker, Miranda Richardson and Phyllis Logan, which is coming to ITV in the New Year while Love, Lies & Records – about the tortured personal life of a registrar played by Ashley Jensen – should be on TV by the time you read this.

Mellor has also flirted with American television, selling her successful BBC1 drama The Syndicate – about a group of lottery winners – to Steven Spielberg some years ago. Executives re-made it for US audiences as a series called Lucky 7, which bombed decisively. Mellor picks through her words carefully. ‘I watched it and it wasn’t exactly... how can I put it politely? Er... it wasn’t what I hoped it might be,’ she says. ‘So am I running over to America again? No. Am I anxious to repeat that experience? Not particularly. But Steven did say to me: “We must talk about movies.” So I may well do that, but I wouldn’t be interested to recreate something else of mine over there. Don’t get me wrong. I’m hugely flattered, it’s wonderful. But my life here is so rich, it’s so lovely. I’m currently writing for ITV, BBC and the stage. What could America do for me?’

Fat Friends the Musical runs at Leeds Grand Theatre from November 7th-December 2nd.

Tour dates include: Hull New Theatre, January 29th-February 3rd; Sheffield Lyceum, February 12th-17th and The Alhambra Bradford May 14th-19th .