“Well, of course all the actual mountain climbing scenes will be done on green screen or whatever, won’t they?”

Sheila Hancock was already sold on the title role in Edie. The story of a recently widowed woman breaking away from the expectation that she would settle into a life of quiet solitude, and instead embarking on a once-in-a-lifetime adventure had touched the 85-year-old actor’s heart.

So when she was told by the film’s producers that, no, there was to be no camera fakery in Edie, and instead she would have to climb Suilven, one of the most challenging peaks in the Highlands, Hancock had a big decision to make.

“There was a terrible silence,” she recalls. “They showed me a picture of this mountain and said they were rather hoping I would climb it. I didn’t know whether I could at my age. I looked it up and it was obvious this was not a thing you should take lightly. But the script had got to me. I loved what it was saying. Whereupon I did a huge, intensive training regime. I was in the gym every day.”

Over the next months, Hancock could be found running up hills with an RAF trainer in Richmond Park, trudging across difficult terrain, and pounding the machines at her local gym. “I enjoyed getting fit and strong,” she says when we meet in central London.

Once the cast and crew of Edie had assembled, it was time for Hancock to put her new fitness to the test. Then there was the small matter of conquering her fear of heights.

“There were bits that were totally terrifying,” says Hancock, describing a narrow section of path with a sheer drop either side in vivid detail.

And not only did Hancock have to tackle this tricky section of Suilven en route to the summit, she had to do it repeatedly – filmed first in close-up, then from various angles, before a final sweeping overhead shot in which she is the only person visible in the vast landscape. Then, at last, the pay-off – achievement unlocked, fear conquered. Or “the incredible feeling of having overcome sheer fucking terror,” as Hancock puts it. She talks of feeling empowered, of reminding herself of her capabilities.

“I think that is the best feeling in the world. To take on something you are frightened of and actually do it – and it doesn’t have to be climbing a mountain,” she continues. “It can be telling your boss you are not happy. Or standing on the street and selling The Big Issue – that must be a hell of a task for some people who are frightened or who have had a tough time. When you find the courage to do that, and then you have done it, I imagine that you get the same feeling I got. Which is that you have climbed your own particular mountain.”

The key themes of the film are, don’t waste your life

‘Choose life’ might be a key phrase from a different Scottish film, but the Trainspotting tagline also speaks to the themes of Edie. After years of fulfilling what she sees as her obligations to her ailing husband – despite years of unhappiness – Edie seizes the day.

“The key themes of the film are, don’t waste your life,” says Hancock. “Because it is never too late. That is what the film says and I am so thrilled it might have that effect on some people. Now I can afford to be a bit more choosy – I do not have to work for the money, which I have had to do all my life – so I am into doing work that says something to people. I am very happy to be in something that seems to be making people feel better or that they want to change their lives.”

Hancock still gets hundreds of letters from people who have been touched by the wit and wisdom of her two bestselling books, The Two Of Us and Just Me, charting her life with actor husband John Thaw and exploring her grief after his death in 2002.

As she works on a third volume – “a summing-up book, about life and what is going on in the world” – she offers insight into loneliness and social isolation affecting more and more older people, the film offers an important message.

“You can get into a habit of feeling lonely, or that everyone has died and left me on my own, but if you look around you, you will find ways of breaking it as Edie does. She is lonely when she is with her husband. She is lonely caring for somebody.

“There are an awful lot of lonely people and I do my damnedest to make them join clubs, go to classes. It is in your hands to turn loneliness into solitude. Sometimes solitude can be lovely. I love being on my own a lot. It is a real effort, even for me, to pick up the phone sometimes. But if I am feeling a bit lonely, it is in my power to phone somebody up.”

The depiction of the developing friendship between Edie and her guide Jonny (Dunkirk’s Kevin Guthrie) – with both learning from the other after initial mistrust – is another aspect of the film that interested Hancock.

“I think it is very sad that at the moment within society, for whatever reason young and old seem to be drifting apart a bit,” she says. “There seems almost to be an anger between the never-had-it-so-good generation and the youngsters who are feeling really hard done by. That is such a sad gulf to have.”

I am heartbroken about Brexit, as heartbroken as any youngster was

Talk turns to the big political issue of the day, the one on which the generation gap was so clear in voting patterns.

“I am heartbroken about Brexit, as heartbroken as any youngster was. And my grandchildren were distraught about it. Anything that breaks links with anyone in the rest of the world to me is suicidal and stupid – I am not talking financially now, just in terms of life. We need to join hands – bridges not walls,” she says.

“But the good thing is that the old people are dying off, you know? Those youngsters will get older and things will change again, I am convinced of it.”

There may be a few more mountains to climb first. But after conquering Suilven, it’s no surprise that Hancock feels the sky is the limit.

“I must say my children’s first question when I get a new part is ‘Does she go senile, or die?’ So it was so refreshing to be able to say, ‘No, she climbs a mountain!’ That was a joy.”

Edie is in cinemas from May 25

Edie

Sheila Hancock on climbing a mountain, loneliness, and Brexit heartbreak