IS there a more enthusiastic musical actress than Bonnie Langford? Bonnie could not have sounded more excited when we mentioned her last performance in York as the Lady Of The Lake, the diva of Monty Python’s Spamalot.

“Spamalot? Loved it! Loved it! Loved it!” she says, recalling her role in the touring production that came to the Grand Opera House last February.

“I had a grand time in it; I did six months on tour, then seven weeks in town [London]. I loved it. Great people to work with – I call them my ‘Spamalee’.”

No sooner had she finished playing the Lady Of The Lake than the very next day she began rehearsals for the first British tour of Dolly Parton’s new musical 9 To 5: The Musical. “So it’s been a tight schedule,” says Bonnie, who will be returning to the Opera House next month to play Roz, the smitten PA to her sexist, egotistical, hypocritical bigot of an office boss, Franklin J Hart Jr.

“Roz is the only one who likes him. She’s besotted with him and she can’t tell he doesn’t feel anything for her. So I’m playing the besotted one, the Shades Of Grey one, who can’t see he doesn’t love her,” says Bonnie.

“She’s very OCD [Obsessive Compulsive Disorder]; she’s absolutely obsessed with writing memos and keeping the office in order. She’s lonely, living alone with her cats and living for the office, but I don’t think you should judge a book by the cover, as there’s something more going on inside her.”

Based on the 1980 movie Nine To Five, the musical features the familiar title number, one song off Dolly’s Backwoods Barbie album and a whole heap of new Dolly compositions. “It’s not just one genre, not just country and western but all sorts of styles,” says Bonnie.

“Everyone knows the title song; it’s gob-smacking how many people know it; people I wouldn’t imagine knowing it do know it.

“Dolly has done a great job on the score and it’s also clever that they’ve still set it in the Seventies when there aren’t many musicals set in that period, a time when the boss was vile to all of his workers, and they get their own back by empowering themselves.”

Bonnie says the reason it is important the show sticks with the Seventies’ setting is that “now, in 2013, you’d be able to get proof in a matter of seconds that the boss is fiddling the books, but in the Seventies that wasn’t the case and so it gives you enough time for a musical – time to fill with a song and a dance”.

It is uncommon for a musical to address the subject of office life – Burt Bacharach’s only musical, Promises, Promises springs to mind – and that makes it stand out from the crowd, reckons Bonnie. “It’s a different kind of show,” she says. “It’s set in an office; it’s fast-paced, quickfire, but also has sweetness to it in the love story of Violet, one of the office workers.

“It also has Dolly Parton turning up on screen at the beginning, in the middle and at the end of the show.”

Bonnie’s big moment comes in a fantasy sequence. “Roz has this fantasy that her boss is in love with her, so it’s all wrapped up in this wonderful farcical situation, which is rare for a musical,” she says.

The scene is typical of a musical that Bonnie recommends you should see with a “light heart. “It’s not a deep piece,” she says. “It’s a show to be enjoyed. 9 To 5 doesn’t have quite the cult following of Dirty Dancing or The Rocky Horror Show, where people shout out the lines, so it’s a smaller cult following, but Dolly has a following and we find that the show really takes off when groups of women come along and empathise with the characters.

“Look, it’s a camp fest. Don’t come if you like Chekhov.”

• 9 To 5: The Musical runs at Grand Opera House, York, from February 4 to 9, at 7.30pm nightly plus Wednesday and Saturday matinees at 2.30pm. Box office: 0844 871 3024 or atgtickets.com/york