When a middle-aged woman in a frumpy dress and sensible shoes walked onto the Britain’s Got Talent stage with a nervous giggle, it wasn’t just Simon Cowell who feared the worst.

“As a Scot, I cringed when she spoke. Anyone who says they didn’t make a judgement when they first saw her is lying,” says actress Elaine C Smith.

Scottish spinster Susan Boyle went on to wow the judges on ITV’s primetime talent show in 2009 and became a star on both sides of the Atlantic. Within days of her appearance, her performance of I Dreamed A Dream, the Les Miserables tearjerker she auditioned with, had been watched online more than 100 million times.

Now Glasgow-born Elaine is playing Susan in a musical about her remarkable story, coming to Bradford next month.

Called I Dreamed A Dream, it follows Susan’s life growing up in a family of ten in a three-bedroom council house in Blackburn, West Lothian, to becoming a global star. Susan will make a guest appearance at the end of each performance.

“The aim is that when she walks on, it will be to a standing ovation. It’s lovely for her to appear. She’s never done a concert tour before so this is her chance to tour the country and see her audience,” says Elaine, 52.

Best known as Mary Doll in popular sitcom Rab C Nesbitt, Elaine says the idea for a musical came from Susan. “In an interview she was asked who she’d like to play her in a movie, and she said me. She’d seen my one-woman show, and she was a Rab C Nesbitt fan,” says Elaine. “There was no chance of me playing her in a film – someone like Cher would get the role – but I saw potential for a musical.

“It was a huge undertaking but in the end the whole machine surrounding her was supportive. Susan was very positive, which was important as it had to be with her blessing. This had to be a great piece of theatre, as a tribute to her.”

Adds Elaine: “My favourite musical is Carousel and I had this idea of Susan looking back on her life, like Billy Bigelow. The narration was a great way of giving Susan a voice.

“I was at Susan’s 50th birthday party and I remember watching her, thinking, ‘this must all be like a dream for her’. For me, this story is about magic and dreams, but not in a sugary sweet way. We tell Susan’s story as it is.”

Susan has described the show as “an honest portrayal of my life”. It starts with her birth, when she was briefly deprived of oxygen. She was later diagnosed as having learning difficulties, and recalls being bullied as a child.

“I wanted to know who was that woman who turned up at Britain’s Got Talent, and where did she come from?

“The first half tells her story, so by the time she reaches that audition we know she had just lost her parents and her sister and was living alone in the house she’d grown up in. She didn’t have her mum to support her and she was lost,” says Elaine. “Her early life makes me cry.”

The rest of the show follows Susan’s extraordinary overnight success.

“When we met I asked how on earth she copes with such immense pressure. I said, ‘I’ve had 30 years to get used to it and I’ve only had 1,000th of your fame’,” says Elaine.

“When she went to America she did 134 TV interviews in a few days. By the time the Britain’s Got Talent semi-final came along, when her voice cracked during her performance, she was exhausted. The Press said she was having a breakdown but she was just really tired and under enormous pressure.”

While the show is a poignant journey through the pain of lost love, tragedy and being cut adrift in life, it also captures Susan’s sense of humour.

Catapulted to fame, her debut album, I Dreamed A Dream, was the UK’s best-selling debut album of all time. It was followed by The Gift and third album, Someone To Watch Over Me. The show combines drama with multi-media technology and the songs from Susan’s albums.

Elaine’s own journey to fame was via Eighties TV sketch show Naked Video. She appeared in TV dramas Two Thousand Acres Of Skye and City Lights, and her theatre work includes Shirley Valentine and Calendar Girls.

Elaine hopes Susan’s inspirational story has marked “the end of judging a book by its cover”.

Since this year’s Britain’s Got Talent has already served up what’s been labelled a “SuBo moment”, in the shape of a shy, overweight teenager with a magical singing voice, it remains to be seen whether or not we viewers continue to judge on first impressions.

* I Dreamed A Dream runs at the Alhambra from April 10 to 14. For tickets, ring (01274) 432000.