Is there a role in musical theatre that covers more territory? It is hard to think of a bigger turnaround than that enjoyed by Eliza Doolittle in My Fair Lady. Following the blueprint laid out by George Bernard Shaw in his play Pygmalion, she starts the show as a penniless flower girl and ends it as a high-society lady. In between, her accent goes from a brash and colourful Cockney to a restrained and plummy RP.

Playing the role of Eliza on a UK tour that calls into the Edinburgh Playhouse for a festive run, Charlotte Kennedy cannot believe her luck. “It’s rare for there to be a role for a woman that has so much depth and growth,” she says. “She’s incredibly clever and is constantly trying to better her life. She is the one who goes to Henry Higgins and says she wants to have lessons. It’s her who’s driving it the whole way through. As an actor, that is a joy.”

Written by Alan Jay Lerner and Frederick Loewe, My Fair Lady tells the story of a flower girl who is approached by Henry Higgins while she is working in Covent Garden. He is a phonetician doing real-world studies of the way people speak. Fascinated by the working-class accent of this "guttersnipe", he makes a bet with his colleague Colonel Pickering. He undertakes to give Eliza all the elocution lessons it takes to pass her off as a duchess at a high-society ball. Little does he realise his protegee will eventually turn the tables on him.

Charlotte Kennedy as Eliza Doolittle in My Fair Lady PIC: Marc Brenner

“What’s fascinating is the way in which she changes those around her,” says Kennedy. “Particularly Henry Higgins – he’s trying to fix her, but in the end, you think, ‘Well, who has been fixed here?’”

Kennedy herself knows all about life’s ups and downs. Like every actor, she has endured feast and famine. In 2016, she was on a high having landed a part in Les Misérables as Cosette, the abused orphan rescued by Jean Valjean. Having graduated from Mountview Academy of Theatre Arts the previous year, she was now making her professional debut in London’s West End.

But even prestigious leading roles must come to an end and, in order for a refurbishment of the theatre to take place, the production closed in July 2019. Kennedy returned to the life of an office temp, squeezing in auditions when she could. “Both of these experiences are as important as each other,” she said on Twitter. “Celebrate the in betweens. Success comes in many different forms.”

Her next break was as sudden as it was unexpected. By now Covid had struck and her industry was under more stress than ever. One morning in the office, she got a call. Could she return to the part of Cosette that afternoon? The pandemic had taken its toll on a concert performance of Les Mis and they needed her to fill in.

“This time a year ago, I was sending out Christmas gifts and booking couriers, so my life has done a 180-degree turn,” she says. “It’s been a wild ride. But you have to go into the profession knowing there is a risk. It just so happened that the pandemic made it so much harder.”

By 2022, the pendulum had swung back in her favour and she had been offered the part of Eliza in My Fair Lady for its UK tour after covering for the part on its London run. Oddly, it seems not to have crossed her mind that the rags-to-riches tale of the flower girl might have parallels with her own life. “That’s a new analogy on me,” she laughs. “I think it’s just life. There isn’t often a rhyme or reason why your life takes a certain path.”

Personal resonance or not, My Fair Lady touches themes about class, poverty and prejudice that remain pertinent. “There are topics at the heart of it that we’re having conversations about more than ever,” she says. “But also, it is a form of escapism. In the economic crisis we’re living through, it lets people forget for a couple of hours.”

Directed by Bartlett Sher, the production started life on Broadway in 2018. The director drew on the original 1913 play and film adaptation as well as the 1956 musical. After the US, it wowed the London Coliseum and has been on the road since February 2022. “Every city you go to, the audiences are slightly different,” says the Northamptonshire actor. “They react to different parts in different ways. There are lines in Cardiff that people find really funny that didn’t have a laugh in Bradford or Dublin. We’re so excited to come to Edinburgh – I don’t think there’s anywhere quite like it.”

What Kennedy loves is not just the meaty plot. It is also the songs, which are performed by a live orchestra. It is hard to beat a musical that offers Get Me To The Church On Time, Wouldn’t It Be Loverly, On The Street Where You Live, The Rain In Spain and And I’ve Grown Accustomed To Her Face.

“The music is the really special thing,” she says. “People are so familiar with these songs. When I sing I Could Have Danced All Night, you see people visibly rise up in their seats. The songs I get to sing every night are some of the best musical-theatre songs ever.”

My Fair Lady is at the Edinburgh Playhouse from 14 December until 7 January

Charlotte Kennedy on playing Eliza Doolittle in My Fair Lady: 'It's a joy'