Rozzi on the right lines to play Bobbie in The Railway Children at the Signal Box Theatre

"Everyone's called me Rozzi since I was seven," explains the Oxford actress, who read Classics at Cambridge "but spent a lot of time at the theatre" as a member of the university's Amateur Dramatics Club.

Rozzi is in York for the summer, performing the role of eldest child Bobbie in the York Theatre Royal/National Railway Museum revival of their 2008 and 2009 productions of Mike Kenny's stage adaptation of the cherished E Nesbit book.

Rozzi had been a member of the National Youth Theatre during her days at Oxford Hight School, acquired an agent while still at Cambridge, and toured the United States with the university dramatics club, playing Isabella in Measure For Measure as they travelled from Nashville all the way up the East Coast to New York and Boston.

She has played such roles as Masha in Chekhov's Three Sisters, Bianca in Shakespeare's The Taming Of The Shrew on a European tour by bus of Paris, Switzerland and Germany, and in her final year at university she found time to take the lead role of Sally Bowles in Cabaret.

Beth Lilly, left, Izaak Cainer and Rozzi Nicholson-Lailey in The Railway Children. Picture: Anthony Robling

Acting is a passion, a vocation, for Rozzi, one where she bucked the family tradition of being doctors, preferring one form of theatre to another. "My great grandfather was a radiologist and doctor; my grandpa on my dad's side was a GP and my parents [Tom and Claudia] are both GPs in Oxford," she reveals. "And my sister Anna is in her first year at medical school!"

So, from where did Rozzi's love of theatre blossom? "My parents took me and Anna to the theatre loads of times when we were young: the Oxford Playhouse, the Royal Shakespeare Company at Stratford, and they'd take us up to London too to see shows."

Rozzi was hooked, the National Youth Theatre and Cambridge university productions ensued, and since leaving university, she has done a variety of theatrical and film work. "I did the BFI Teenage Kicks season, doing a couple of short films, such as Aquarium, a funny story about a fish tank, and I've also been involved in the National Youth Theatre, doing research and development on new projects and rehearsed readings," she says.

Rozzi Nicholson-Lailey in The Railway Children. Picture: Anthony Robling

"I've done some fund-raising for them too, singing at fundraisers. Most recently we were singing in The Queen's Music Room at Buckingham Palace in the spring, when Prince Edward attended."

In the spring too, Rozzi auditioned in London for Damian Cruden's 2015 production of The Railway Children in the 1,000-seat Signal Box Theatre at the NRM, a traverse design with a track down the middle and ten rows of seating either side. "My agent told me about it only a couple of days before the auditions. so I did the audition and two days later I'd got the part," she says, gratefully.

Rozzi had not seen either of the NRM productions, nor the London stagings of Kenny's adaptation, and she decided against attending the present run at the King's Cross Theatre. "Once I knew I had the role, I just wanted to re-read the book and the script," she says. "I'd read the book as a child, and I found my original copy again, in which I'd written something like Rosalind Nicholson-Lailey, Class 2.0!

"I loved the Mike Kenny script, which is moving but it's so funny as well, which is not something you think of first with The Railway Children. It's a brilliant script and it's so nice to come to York for the summer to perform it.

Rozzi Nicholson-Lailey and Robert Angell in The Railway Children. Picture: Anthony Robling

"Though I have no connections with the city, I do remember coming up here when I was about ten and we went to the NRM and the Jorvik Viking Centre, of course!"

Rozzi is performing on a traverse set for the first time, so she took the opportunity to watch the York community play, In Fog And Falling Snow, on the same design, but she does have experience of playing a young character. In this instance, the 22-year-old Rozzi is playing Bobbie in her early twenties looking back on her days as one of the railway children when she was 12.

"The youngest role I played at university was Thomasina Coverly in Tom Stoppard's Arcadia, one of my favourite plays ever. She starts off at 13 and is 15-16 by the end. That was in my first year at Cambridge."

Analysing Bobbie's character in E Nesbit's story, Rozzi says: "The main thing about Bobbie is her capacity to understand, and her empathy for her mother is huge. She doesn't know what's happened to her father, but she absorbs so much, always noticing how her mother feels, maybe more than any other 12 year old would do. That's something unique about her."

The York Theatre Royal/National Railway Museum production of The Railway Children runs in the Signal Box Theatre, National Railway Museum, York, until September 5. Box office: 01904 623568 or at yorktheatreroyal.co.uk