When Margaret James goes shopping in Wimborne, people will sometimes come up to her and say excitedly: “I saw it again today!”

They are referring to one of Britain’s best-loved films, David Lean’s 1945 masterpiece Brief Encounter, whose 70th anniversary was marked last year.

“It’s extraordinary,” says Margaret, who at 89 is the last surviving member of the film’s cast.

Margaret was 19 when she was chosen, without an audition, for the role of Beryl, the girl in the railway station refreshment room, which is the main setting for Noel Coward’s story.

No one forgets the character’s name, because of the haughty way Joyce Carey as the manager, Myrtle Bagot, snaps “Ber-yl!” at her.

Beryl, Myrtle and Stanley Holloway as station master Albert Godby are the comic relief, around which Coward tells the story of two married people who begin an innocent friendship and fall in love.

“The three of us were the comedy section,” says Margaret, whose surname then was Barton.

“I’ve often been asked, ‘Did you know that this great love affair was going on at the table?’ I say we didn’t know. They were just customers with their cups of tea and cake.”

Margaret had been acting since the age of 12, when she worked with the famous actor-impresario Donald Wolfit.

She recalls: “David Lean and Noel Coward had seen me during the war in lots of London plays, had heard me on the radio and they said, ‘That’s the girl we want to play Beryl in the refreshment room’.”

Filming took place at Denham film studios in April 1945.

“David Lean used to ask me to come behind the camera sometimes and see what Celia Johnson and Trevor Howard were doing in their scenes,” Margaret recalls.

She was impressed by Johnson, who narrates the story of the forbidden romance which unfolds over several Thursday afternoons.

“There was something that captured you when you saw Celia close up,” says Margaret.

“She was right in the part.

She was never out of it.”

The two were to become friends later.

“I went off on tour with Celia in the early 1950s with the Arts Council, to do Shakespeare. We did Twelfth Night. She made a lot of lovely films,” says Margaret.

“There was nothing showy about her, she was lovely. She was a nice friend.”

Margaret had less chance to get to know Trevor Howard, but has fond memories of Stanley Holloway.

“He was a great comedian. He used to keep us amused while we were waiting for the scenery or the lighting to be changed,” she says.

Margaret remembers the film getting some indifferent reviews when it came out that November, but before long it was on its way to being cherished as a classic.

“It was my first film and I did about nine or 10 films altogether through the 1940s,” she says.

“One particular favourite is Temptation Harbour with Robert Newton and Simone Simon. I had a wonderful part in that.”

She continued to act on stage, including a long run in Spider’s Web by Agatha Christie, before giving up acting to raise her son Michael.

Michael, a gifted organist, pianist and teacher, died when he was just 30.

“You don’t get over it. You learn to live with it,” says Margaret.

“I think about him every day of course and wonder what he would be doing now. He would have been 64.”

In his memory, Margaret and husband Ray set up the Michael James Music Trust, which gives financial support to young musicians, currently funding organ scholarships at around 12 colleges.

Margaret remains in demand thanks to Brief Encounter and was invited to open a replica of the film’s refreshment room at Carnforth Station Heritage Centre in Lancashire, whose platforms and clock feature in the film.

Why do people still love Brief Encounter?

Margaret’s answer begins with the way Lean deployed Rachmaninov’s Piano Concerto Number 2.

“I think if he had chosen anything else, it would have not been the same thing at all.

“The other thing is it’s a nostalgic way of looking at the past. It was a lovely time and I sense people today have a feeling for the solid things in life.

“You didn’t just jump into bed with each other. You didn’t do things like that, you held on to the true things in life.”

Audiences young and old still respond to the movie.

“They come with their handkerchiefs because they know they’re going to cry at the end,” says Margaret.

“They know the story, they’ve seen it so many times and yet they want to see it again.”