To recap on her career so far: In 1998, while still at school, she was plucked from obscurity by Andy McCluskey of 80s band Orchestral Manoeuvres In The Dark, who auditioned her for manufactured pop group Atomic Kitten.
She teamed up with Heidi Range and Kerry Katona to form the trio, before Natasha Hamilton replaced Range, ahead of the group’s debut single, Right Now, going Top Ten in 1999.
The girls would go on to notch up three No1 singles and two chart-topping albums, selling more than ten million records.
McClarnon was the only remaining original member when the band officially split in 2008, after which she launched a solo career that saw her chart with a cover of Barbara Steisand’s Woman In Love.
But after failing in her bid to represent the UK in the 2007 Eurovision Song Contest, she turned her back on the pop world and focused her attentions on theatre, winning the role of Beth in Jeff Wayne’s version of The War Of The Worlds.
The singer-turned-actress got a real buzz from being on stage in a big theatrical production, which is why she’s relishing her role in the touring version of Legally Blonde, which comes to the Playhouse on a ten-night run next week.
Explaining how she came to be cast in the production, McClarnon says, “I’d known the casting director for a long time, and he basically told me to go and watch the show, which I did. Then, during the interval, he said ‘what’s your favourite character?’ I went, ‘Oh, I love Paulette’, and he asked me if I wanted to play her.”
McClarnon didn’t need to be asked twice.
She was already a massive fan of Legally Blonde, the hit movie starring Reese Witherspoon, on which the musical is based.
“I’ve seen it millions of times,” she says enthusiastically. “It’s a really good film - wicked.”
Legally Blonde centres on spurned college sweetheart and homecoming queen Elle Woods, who isn’t the type to take no for an answer.
When her boyfriend, Warner, dumps her for someone serious, Elle puts down the credit card, hits the books, and heads for Harvard Law School, determined to prove she’s more than just a pretty face.
The all-singing, all-dancing, musical-comedy has been a big hit with audiences since it launched its UK tour, and McClarnon has attracted glowing critical praise for her role as hairdresser Paulette.
“It’s going so well,” she says. “We’re getting standing ovations every night and everyone who comes along seems to love it.
“It’s hard work but so much fun - so enjoyable,” she continues. “The cast get on brilliantly and we have a real laugh together. You can’t ask for any more, can you?”
McClarnon, who won Celebrity Masterchef in 2008, and is set to release her first cookbook later this year, feels a real connection with her character. “She’s a hairdresser from Boston, and bit unlucky in love,” she says. “Oh, and a bit fat.
“I guess Paulette tries to see the best in everyone, though it never really turns out well for her. But she’s sweet, endearing and funny.”
The former pop idol says working in theatre and being in a pop group are like night and day. “It’s very different,” she explains. “With theatre you’re working every night, whereas when you’re in a group like Atomic Kitten, at least when you get really big, there are times you wouldn’t sing for a while. There were days when we were doing other things... branding, photo shoots, etc.
“In a musical production you sing every night, and that’s what you do. End of.”
Though she’s loving her current job, McClarnon won’t rule out an Atomic Kitten reunion somewhere down the line - though she feels the group called it quits at the right time.
“We were all quite tired, and I do think it was time to end it,” she says. “It absolutely was the right decision - we got out of it with our friendships intact and we all still love each other.
“As for a reunion? I’d say ‘never say never’, but only because we all get on so well.”
McClarnon is still on very good terms with Katona in particular, who is currently appearing in Celebrity Big Brother. So has she had a chance to watch her old pal on the reality-TV show?
“I haven’t been able to watch any of it yet, because I’ve been working with the show every night,” she says. “But I’ve got it all recorded at home, and I’m planning one big marathon viewing session when the tour finishes.”
Legally Blonde, Edinburgh Playhouse, Greenside Place, Tuesday to September 14, 7.30pm (Wednesday and Saturday matinees, 2.30pm), £22.50–£59.50, 0844-847 1660