WHEN Kay Mellor spotted a girl spilling out of a purple dress holding court outside a Leeds nightclub, she knew she had the lead character for her next TV drama, Fat Friends.

“She was standing outside the old Town & Country Club, it was a chilly November evening and she wore a purple Lycra dress, no coat and white heels. Her hair was platinum blonde and she was Queen Bee - a big, confident girl, surrounded by skinny girls hanging on her every word,” recalls Kay. “She seemed such a positive image of a bigger young woman. That’s where Kelly came from.”

Kelly is at the centre of Fat Friends the Musical, Kay’s stage version of her much-loved TV series. The Super Slimmers are struggling with the absurdities of modern dieting, and Kelly is counting the days until her wedding day. It's what she has dreamed of all her life - but her mother, Betty, a champion slimmer who can't eat a lettuce leaf without fretting, is trying to encourage her to shed the pounds for her big day.

Headstrong Kelly is happy with the way she is, and fiance Kevin insists he likes her that way. But when she can't get into her dream wedding dress - and hopelessly romantic boutique owner Lauren says they don’t make the dress in her size - Kelly uses all her wedding savings to buy the dress anyway, even though it's two sizes too small.

Will she succumb to pressure from Betty, and Super Slimmer chief Julia Fleshman, who spies an opportunity to turn Kelly into a social media hit?

Bafta-winner Kay wrote and directed the show, featuring songs by Nick Lloyd Webber (son of West End king Andrew). The cast includes Jodie Prenger, as Kelly, former X Factor winner Sam Bailey as Betty, Bradford actress Natalie Anderson as Lauren, Natasha Hamilton of Atomic Kitten as Julia and, in his first musical role, cricket hero Andrew "Freddie" Flintoff as Kevin.

"I'd always wanted to do a musical, I've seen a million of them but had never written one," says Kay. "I soon realised that musical theatre is a whole different medium to what I was used to. I didn't want to do a play with songs, I wanted it to be a proper musical. I worked closely with Nick, who taught me things like what a bridge was, and when to use one."

When it came to adapting her TV series, Kay looked to social media. "The slimming industry is huge online. It all adds to the pressures we face to look a certain way. The message of this show is to embrace who you are," she says. "I talked to Dawn French about it, she said when she got married everyone kept telling her that brides always lost weight for their wedding day. Why do we feel the need to become someone else for that big day?"

Leeds-born Kay has a soft spot for Bradford and several of her TV dramas, including Band of Gold, The Syndicate 2 and The Chase, have been filmed in and around the city.

More recently, Kay has created TV dramas In The Club, about a group of expectant mums meeting at ante-natal classes (the second series saw them coping with motherhood in various ways), Love, Lies and Records, set in a Leeds register office, and Girlfriends, about three middle-aged friends who support each other through crises, part of which was filmed at Bradford College.

"I'm a Leeds girl but Bradford feels like home," says Kay. "I love it, it's very filmic. I love the fantastic buildings; the masculinity of the stonework against the rolling hills. Each building has its own story. And Yorkshire people are great storytellers; that's where I get my inspiration from."

* Fat Friends the Musical runs at the Alhambra from May 14 19. Call (01274) 432000.