Playing Mrs Johnstone is in the blood for New Seekers singer Lyn Paul

So began a near 20-year association with Willy Russell's musical Blood Brothers, whose latest tour under Bill Kenwright's management brings Lyn to the Grand Opera House, in York, from Monday to Saturday.

"I didn’t know Bill although I knew Carl Wayne, who was the Narrator in the London show at the time, and he came to see me in a cabaret show I was in down the road from the Phoenix Theatre and he told me, 'You know, you should go and audition for Mrs Johnstone'," she recalls.

"I didn’t even know Blood Brothers, so I asked him about it and said, 'I can’t, I don’t act'. But he said I should give it a go. So I went back and discussed it with my mum and she said, 'Oh, Bill Kenwright, he’s a very nice man'. I said, 'How do you know, you’ve never met him', and she said, 'Well, I’ve seen him interviewed and he’s a very nice man, write to him!'. Typical northern mum!

"So I did, I wrote and just said, 'Would you consider seeing me for the role of Mrs J; I’m not Liverpudlian but I can get into the accent', gave him all that, and I posted it off. Two days later I got a return letter saying, 'Don’t worry about the Liverpudlian accent, love, we’ll sort that, you don’t need one, you’re a Northerner, and I’d love to see you'."

The year was 1997, and after that letter by return post, less than three weeks later Lyn was waiting on the stage at the Phoenix Theatre to start rehearsals, switching from the cabaret circuit to the West End. "I’d never acted and I thought, 'oh my god, I can’t do this', but Bill showed so much faith in me," Lyn recalls.

Her Blood Brothers debut ended up being a little sooner than first planned. "I was rehearsing to open in London on the Monday, but then I got asked if I knew it well enough to do the last night in Birmingham as Stephanie Lawrence had fallen ill," says Lyn. "So I went up there, did the show and came straight back down to London to start on Monday."

Lyn duly played Mrs Johnstone from 1997 to 2000, returning to the role in 2008 and 2012 for the final two weeks of its West End run, as well as doing several tours. She is back in the show once more at the age of 67.

Lyn Paul as Mrs Johnstone with the Blood Brothers cast in a previous production

"The role hasn't changed over the years. The producers are sticklers for keeping it as it is and I think that's a good thing. If I see someone coming in and trying to change things, that can be irritating, as the show has always worked so well for so long, why change it?" says Lyn.

"They call this show a rollercoaster of emotion and it is. One moment, the audience are laughing, the next they're crying, and Willy Russell has a real art for that in Educating Rita and Shirley Valentine, as well as Blood Brothers. He pulls at the heartstrings very subtly. Blood Brothers is very touching, but he keeps it raw so it's not maudlin."

Returning to playing Mrs Johnstone again after two and a half years is like greeting an old friend, albeit an initially terrifying prospect, says Lynn. "I will treat it like a new show. Obviously it’s easier because I do know what I’m doing and because it is so well directed. When I first started, it was directed by Bill and also Bob Tomson, so all those notes I have I’ve still got written down and a lot of that will come back to me because I think the way they directed it is just second to none."

Lyn considers Mrs Johnstone – the mother of twins separated at birth but fated to cross paths to their dying day – to be her ultimate role in a stage career that has taken in starring in Cabaret alongside Will Young. "Mrs J is just me. Everything that she’s going through I feel," she says. "I can relate to her so well, being a Northern mum and having gone through a lot of struggles in my life, lots of lows. I can relate to her to a great extent."

So much so that when Bill Kenwright comes calling, "I will always go back," says Lyn. "He’s only got to click his fingers and I’ll be straight in, no problem."

Summing up Mrs Johnstone's characteristics, Lyn says: "She's stoic, she's kind, generous spirited. She's a very strong, grounded, working-class woman, which is me down to a T: I was born on a Manchester council estate, the eldest of six children."

Her mother had a lovely mezzo soprano, her father could sing in the Frank Sinatra style, but neither sang professionally. Nevertheless, from a nursery school teacher's suggestion that Lyn should go to dance school, a life in performance was set in motion. "If you heard me at 13.14, 15, you wouldn't have thought I would become a singer," she says, but how wrong she was.

Blood Brothers runs at Grand Opera House, York, from Monday to Saturday, 7.30pm and 2.30pm Wednesday and Saturday matinees. Box office: 0844 871 3024 or at atgtickets.com/york