Emma Thompson's Red Road journey with Robert Carlyle

If viewers aren’t moved by the landscape they’ll feel the pain of the film’s title character, brought to life by the actor, who suffers a soul-destroying barrage of vitriol from his mother, played by Emma Thompson, who turns in a remarkable performance as Semolina, a foul-mouthed 77-year-old ex-prostitute.

“It was such a satisfying scene to shoot,” she recalls when we catch up ahead of the film’s release.

“It is so powerful and it is funny but also brutal, really brutal and it says everything you need to know about how these two people have been brought up and how they have had to cope with the violence that would have been part of their lives.

"I added some flinches so that you know that when she was a baby she was thumped, really badly. It is tragic.”

the actress, who has a deep connection to Scotland, recognised the importance of the Red Road backdrop. “There is just nothing there at all,” she says, “they’re totally marooned in a concrete wasteland.

"Some of the props littered around the waste ground are quite heart-breaking, like the wee teddy bear. That really spoke to me.”

In truth, there were many aspects of the film that spoke to her, not least her admiration for Mr Carlyle, who proved his mettle by not only overseeing the film with expert direction, but also by playing the title role.

She has long been an admirer, sending him a postcard early in their careers, even before he’d hit the headlines with his memorable turn as Begbie in Trainspotting, expressing her admiration for his talent.

“I do that a lot,” she says.

“If I like something, I generally will write to someone because it is nice to get it off your chest if you haven’t got the chance to go see them.

"It is something I have always loved doing. I am a wee bit older than Bobby but we are more or less contemporary (she's 56, he's 54). I can’t remember which film is was for though.”

Whatever the film, he was touched by the gesture and remembered her note across the years.

When he wrote to her about the Semolina role, he included a letter with the script saying how much that card had meant to him.

“He is an amazing bloke,” she says, “an absolutely extraordinary bloke, and it was such a treat that he was directing as well acting because it meant that he was there all the time and we had access to him and to the way he thinks. He’s such a great thinker.”

Like Robert Carlyle, Emma Thompson has Glaswegian roots.

She was born in London but her mother, the actress Phyllida Law, hails from Glasgow and she spent a great deal of time in Scotland during her youth.

“I was there a lot when I was growing up and until I went to school because my grandparents lived there and I had an uncle who ran a tea room in a village called Ardentinny until I was 15, so me and my sister would help out in the tea rooms, and we spent all our holidays there with the family.”

The connections continue – her husband, actor Greg Wise, bought all the furniture for his flat from the Barras when he was living and working in the city back in the day, “and we’d visit the Barras for bits and bobs for where we stay in Scotland,” she recalls.

“My mum went to the Barras quite a lot with dad when she bought a little croft that we still stay in and was furnishing it for as little as possible.

"The Barras in those days was absolutely remarkable. The market bit now isn’t the same as it was but it has still got its feel and its roots.

“We were always on the coast, or on the lochs so we rarely went into Glasgow, except when I was teeny and my gran still lived there.

"I have worked in Glasgow a lot, though, and I love the city very, very much.”

That said, the overriding attraction of The Legend of Barney Thomson, she concedes, was the character Semolina.

“I loved the very badly applied mascara and lippy on her teeth,” she smiles.

“All of us in make up and prosthetics were sniggering to ourselves.”

The actress spent more than five hours in the make up chair each day as the extensive prosthetics were applied and removed.

Not since her 2003 turn in Angels of America, where she played one scene as a tramp, had she worn so much facial padding.

Even her performance in the two Nanny McPhee films didn’t require as lengthy a transformation as did The Legend of Barney Thomson, where the actress gains more than 20 years in age.

“She is one of my favourite parts, one of the best that I have ever played. I just adored it,” she says of the Semolina role.

“It was an amazing experience. As soon as read the first few pages of the script and I came across the line about Barney looking like a haunted tree that absolutely sold me. I didn’t even wait, I just rang up my agent and said, ‘I have got to do this.’

Emma Thompson’s career began at the Fringe back in 1981 when she and fellow Footlights performers Stephen Fry, Hugh Laurie and Tony Slattery won the first-ever Perrier Comedy Award for their self-penned The Cellar Tapes.

Writing has remained a presence in her professional life ever since, and on the big screen in particular she’s enjoyed some phenomenal successes, following Sense and Sensibility with another adaptation, Nanny McPhee, and an original sequel, Nanny McPhee Returns.

She also wrote last year’s drama film Effie Gray (in which she also acted) and has penned two Peter Rabbit books.

“I feel like I have never stopped, really,” she says of her work.

“I have stopped for family reasons but that is not stopping. That’s doing something else equally stressful, which I personally think is harder.

“I now might try to write Nanny McPhee, the musical,” she adds when we talk about writing projects.

“I would really like to do that because the film was originally going to be a musical.

"There’s a romantic comedy I want to try as well.

"I am very likely to spend the rest of this year and next year writing because I have done quite a lot of acting this year.”

Her acting this year not only takes in The Legend of Barney Thomson, but also Beauty and the Beast for director Bill Condon, a live-action re-treading of the animated Disney musical.

She lends her voices to the warm and cheerful teapot, Mrs Potts, though she also gets to sing and dance in a big final number once the curse on the prince is lifted and the staff members are released from the spell that morphed them into household objects.

She also takes a supporting role in Adam Jones, which features an all-star cast led by Bradley Cooper as an overstressed chef.

A more prominent role, meanwhile, comes with Alone in Berlin, an adaptation of the celebrated 1947 novel by German author Hans Fallada, which is based on a true story.

“It is an extraordinary book and it is an era that has always fascinated me,” she says. “When I was working on The Remains of the Day I did an awful lot of work on that period.

“Making Alone in Berlin was a great privilege, as was working with Bobby on Barney Thomson. I’ve been very lucky to have such wonderful opportunities.”

The Legend of Barney Thomson (15) is out on July 24