Sir Paul McCartney on his late wife Linda's photography ahead of Glasgow exhibition

Yet, more than that, it is a place that resonates with love, one where Sir Paul, his late wife Linda and their young family were able to enjoy normality away from the spotlight.

It is a period of their lives that will be celebrated when a retrospective exhibition of Linda McCartney's photography opens at Kelvingrove Art Gallery and Museum in Glasgow this Friday, marking its first showing in the UK.

Speaking exclusively to The Herald Magazine, Sir Paul, 77, reminisces about their time spent at High Park Farm near Campbeltown and what Scotland means to him.

Looking through the photographs, happiness is a word that immediately springs to mind. Is that how he felt in Scotland? "Very much so," he says. "It is funny because the first time I really heard anyone talk about it with a lot of fondness was John Lennon.

"He had relatives up in Scotland who he liked a lot and he visited them when he was a kid. He would talk with great fondness of the crofts and the holidays he'd had up in Scotland. So, there was always a nice feeling about it for me.

"Then, when I ended up getting the farm at Mull of Kintyre and going up there and spending some time, it had the same kind of resonance for me. Again, it was this fondness for the people and for the land. It constituted a form of freedom for us.

"We could get away from all the things we normally did and just enjoy a lot of space. One thing about the farm was you could walk out at night and see 360 degrees of sky which you can't do in a city."

Sir Paul purchased High Park Farm in 1966. The farmhouse, atop a hill overlooking Machrihanish Bay, came with 183 acres.

He married Linda three years later and the farm became a beloved haven where the couple's growing brood of children could play, swim, ride their ponies and, most importantly, enjoy a semblance of a normal life.

Linda's photographs offer a tantalising window into that time. "There is the one of me on the fence with two of my kids," says Sir Paul. "I think it captures the free spirit that we enjoyed when we came to Scotland. We escaped a lot of business stuff that was going on in London.

"That picture shows the joy of being in the freedom of Scotland. The baby is Mary and the one hanging over the fence is my eldest daughter Heather."

Another image shows Mary, snuggled inside her father's jacket with only her little face peeking out. Love shines in his eyes, undoubtedly directed to the woman behind the lens.

When I mention what a special shot that is, Sir Paul responds delightedly. "It is," he says, a smile in his voice. "I use that shot in my concerts. In the shows I am doing currently [his Freshen Up tour] we put it big on the screen behind me.

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"When I am doing one of my songs, Maybe I'm Amazed, because it was written around that time, I always say to people: 'You know that baby in my jacket? That baby has got four kids of her own now.'" He chuckles softly. "That is a lovely picture."

Nature and stunning scenery abound in Linda's photographs. Sir Paul recalls how, when they first moved to the farm, the couple taught themselves about looking after the land and animals.

"That's true," he says. "It was learning as we went along. What we did was kind of busked a lot of it. But we also asked neighbours, local people and friends: 'How do you do this?'

"I remember wanting to lay a floor with concrete. I would ask a local guy and he would show me the basics and then I would finish the job myself. It was great. Yeah, there was a lot of learning, but it was really good."

Kintyre provided a much-needed bolthole away from London during the late 1960s and early 70s. "The problem was a lot of business troubles going on with The Beatles and the precursor to The Beatles breaking up," he says. "An American businessman [Allen Klein] had come in and it was the beginning of the end. We had this idea to escape – and we escaped to Scotland."

Despite these tumultuous times, there is an infectious, carefree joy that radiates from many of the photographs. Among the collection is a shot of a laughing Sir Paul carrying a brown paper bag as he crosses the road.

"I think that was in Glasgow," he muses. "I had just bought a bottle of whisky and was walking back to my Land Rover. I seem to remember we were driving back down south. I would have stopped off in Liverpool and had a wee dram."

There are self-portraits of Linda, some with an almost dreamlike quality. I ask if Sir Paul has a favourite. He admits it's simply too difficult to choose. "A lot of those portraits, of the Scottish ones, she would say: 'Here, you take a picture of me' and would just give me her camera," he recalls.

"Of the actual self-portraits that would often be her taking a picture in a mirror because, of course, you couldn't do what you can these days, which is turn the camera screen round so it is pointing at you. The equivalent was always in a mirror. There's a lot of nice little self-portraits."

The retrospective includes one of Linda's diaries from the 1960s, displayed for the first time, bringing fresh and fascinating insight not only to the music scene of the era, but also the beginnings of her photography career.

Born in Scarsdale, New York, Linda studied art history at the University of Arizona. Remarkably, the extent of her formal training in photography comprised just two lessons at night school. Seeing the work of influential American documentary photographers Walker Evans, Dorothea Lange and Edward Weston is credited with inspiring her.

Linda's big break came while working as an editorial assistant at Town and Country magazine. She used an unwanted invitation to a Rolling Stones promo party on the Hudson River to take pictures of the band. Following the success of the images, Linda became a professional photographer.

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Her early focus was on capturing the music revolution of the sixties. As the resident photographer at Fillmore East in New York, she took pictures of many of the greats: Otis Reading, BB King, The Doors, The Grateful Dead, Frank Zappa, The Who and Jimi Hendrix among others.

In 1967, Linda was voted US Female Photographer of the Year and soon afterwards became the first woman to have her work featured on the cover of Rolling Stone magazine with a portrait of Eric Clapton.

It was while on assignment in London to shoot the "Swinging Sixties", that she first crossed paths with her future husband in 1967. Linda and Sir Paul met at the Bag O'Nails music club, then again, four days later, at the launch of The Beatles' album Sgt. Pepper's Lonely Hearts Club Band.

The couple married at Marylebone registry office in London in 1969. Alongside her photography, Linda enjoyed musical success as a keyboard player and vocalist in Wings with Sir Paul and the former Moody Blues guitarist Denny Laine in the 1970s.

Among their most famous songs was Mull of Kintyre, a tribute to the landscapes that brought solace and inspiration. Released in 1977, it was a Christmas number one and spent nine weeks at the top of the charts. The track featured the bagpipes and drums of the Campbeltown Pipe Band.

Linda went on to write and record several songs, including Seaside Woman which was released in 1977 under the pseudonym Suzy and The Red Stripes. Wide Prairie – a collection of her recordings – was released posthumously in 1998.

A passionate animal rights campaigner and a pioneer in the vegetarian movement, she became a successful cookbook author, breaking new ground by launching her eponymous range of ready-made meat-free meals in 1991.

Linda continued to work prolifically as a photographer until her death from breast cancer in 1998. The retrospective of her extensive archive was first shown at the Kunst Haus Wien in Vienna and then Montpellier's Le Pavillon Populaire and Daelim Museum in Seoul.

Curated by Sir Paul alongside his daughters Mary and Stella, themes include The Sixties, Family Life, Self Portraits, Observations – Animals and Nature, and Scotland.

Does Sir Paul plan to pop along when it goes on show in Glasgow? "I hope so," he says. "I won't be able to be there for the opening because I have some concerts. But hopefully during its run I will be able to get in there. I'm excited about it. We are all excited.

"It's one of those cities we love. I passed through it a million times on my way to 'the wee toon' – Campbeltown. We would drive up from London to Liverpool, stop off and stay the night, before the rest of the journey.

"Coming through Glasgow was like arriving because you knew from there, you would just turn left at Loch Lomond and go right down the peninsula and it wouldn't be long until you were on holiday.

"It was always great fun coming to Glasgow. Of course, we played there with The Beatles. And since a lot of times. So, we always had a great affection for it."

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At times, there is a wistfulness as he speaks. Yet these are clearly memories that Sir Paul enjoys conjuring in his mind's eye. Memories caught on camera by Linda.

"Another favourite is the one of me standing on the fence with young James jumping off the bonnet of the Land Rover and Stella crouching in the foreground," he says. "That's a lovely picture and I always mention it because it was the perfect moment to click.

"If it had been taken two seconds later, it wouldn't be as good a picture. It is just one of those moments in time that is captured and says it all. I think that shows Linda's great skill as a photographer."

We talk a bit more about the inimitable skill and presence that Linda brought to her work. Love, warmth and an inquisitive eye come across in many of her pictures. She had such a lovely knack for capturing a beautiful moment, didn't she?

"I think that is a lot to do with it," says Sir Paul. "Great photographers know what to look at. If you look where you are – or anyone looks where they are now – you can look anywhere in the room, but a great photographer will see the photograph.

"It is often to do with lighting or people or situations. I'm looking in the room I'm in now and there is one corner of the room that for me, that is where you would want to photograph. That is always the big thing, knowing what to look at.

"The other thing is knowing the exact moment when to click the shutter. There is a lot of other things; you have got to get your lighting right.

"One of the great skills of Linda's was making a person feel at ease," he continues. "Some photographers you feel very stiff with and are not comfortable.

"Whereas, if you have a photographer like Linda or Mary – our daughter has got this knack too – you just feel like you are talking to someone, enjoying yourself and having a conversation. And, oh, incidentally you are having your picture taken.

"That comfort is a very big thing. If someone can put you at ease that is another skill that a good photographer needs. I think the exhibition proves that Linda had a lot of these skills rolled into one."

Sir Paul, Mary and Stella sat down with their Scots-born archivist Sarah Brown to sift through the photographs and make their selection.

"We really enjoyed looking through the pictures, saying: 'Oh, I love that one, that one has to go in, that's a great one.' Especially when it came to things like the Polaroids. There are so many of those pictures and we each had our favourites," he says.

"It is really good having this exhibition in such a cool gallery in Glasgow. Having the person co-ordinating it be a Scot who is very familiar with Linda's work and very knowledgeable about photography, it all worked out great."

There was plenty of happy reminiscing during that process. "With the kids a lot of their childhood was spent there," he says. "We took a lot of holidays and spent a lot of time there when they were little. So, they do have fond memories and nostalgia for the place.

"That is another nice thing about the exhibition for us. You see a picture and think: 'Oh my God, I remember that.' There is one, a picture of a group of old men in their raincoats. The locals used to call them 'the old biddies.'

"'Hey, there's the old biddies on the corner.' They were these old guys with their walking canes. They used to meet up, sit on the bench and just watch life go by. They had on their little caps and long raincoats.

"Every time you went into town, you would see them. You would pass them and wave to them. Those are the kind of things that are long gone, so they are beautiful memories."

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There has been a sense of pride in seeing the exhibition come together. "The whole family loves to honour Linda's work. She would have loved this because Glasgow was a place she loved.

"She loved Scotland because it gave us a lot of fond memories, a lot of freedom and a lot of happy times. It is nice to have all of that encapsulated in the Kelvingrove exhibition."

The Linda McCartney Retrospective opens at Kelvingrove Art Gallery and Museum in Glasgow on Friday and runs until January 12, 2020. Tickets cost £7 for adults (£5 concessions) with entry free for under-16s. Visit glasgowmuseums.com