“I do sometimes think, ‘Wait a minute! I was one of The Beatles! Can you believe that?’” Sir Paul McCartney tells Stellar with a laugh.

“I was one half of the Lennon/McCartney songwriting team!

“Occasionally these things occur to me. Normally it’s just something I take for granted, but sometimes I look at it and think, ‘Bloody hell, it’s amazing.’ Then I get right off it before my head explodes.”

The figures are enough to warrant cranial expansion: 800 million albums sold by The Beatles alone; 30 American No. 1 singles; 2200 cover versions of ‘Yesterday’; 21 Grammy awards; and a fortune estimated to be more than $1 billion.

Yet McCartney remains the music world’s most modest genius.

This year marks the 60th anniversary of a 15-year-old McCartney joining The Quarrymen, a band started by John Lennon. In 1960, they renamed themselves The Beatles and went on to change not just the way music was made — but literally change the world.

“You start off trying to achieve something,” McCartney tells Stellar in his only interview with an Australian publication.

“When John and I met I said, ‘One of my hobbies is writing songs, I’ve written a couple of songs.’ He was the only person I’d ever met who said, ‘Yeah? So have I.’ So when you think of those real humble beginnings, of the two of us showing each other the little songs we’d written, then starting to write together, it is amazing that we carried on and went from strength to strength.

“We wrote songs that people actually know and love and are really famous around the world. I do sometimes think, ‘Blimey.’ Obviously I’m really very proud of it. I can’t believe my luck. Not only did I get to do it for a living, I ended up being pretty good at it.”

This December, McCartney will bring those “pretty good” songs back to Australia for the first time in 24 years.

“Raising kids” is one reason he uses to explain the long absence from our shores.

“Now they’re pretty much all grown up, some with kids of their own,” he says.

“I’ve managed to find a window.”

Stretching over two and a half hours, his live show is an even mix of songs by The Beatles and his other band Wings, along with his solo material.

On most nights, he shoehorns in ‘A Hard Day’s Night’, ‘Blackbird’, ‘Jet’, ‘Love Me Do’, ‘We Can Work It Out’, ‘The Fool On The Hill’, ‘Let It Be’, ‘Live And Let Die’, ‘Eleanor Rigby’, ‘Something’, ‘I Saw Her Standing There’ and ‘Yesterday’.

Having to work out which stone-cold classics to leave out is a superstar’s first-world problem.

“I sit down before a tour and think, ‘If I was going to this show, what would I definitely want to hear?’” McCartney explains.

“So I write down the songs where the show wouldn’t be the same if ‘he’ didn’t play them. Then I start thinking, ‘Well, a lot of people might not know this one, but a lot of Wings fans will know this one.’ I try to put stuff in for people who want a little more depth. You’re trying to give people value for money.

“I remember very well when I paid my hard-earned money to go to a show and ended up feeling a bit cheated. Even when the economy is doing well, and now when it’s not doing well, people spend a lot of money on the tickets. I want them to go away and think, ‘You know what? That was worth it.’”

McCartney is currently making his 17th solo album — the first since 2013’s New, on which he worked with producers Mark Ronson (Amy Winehouse, Bruno Mars), Paul Epworth (Florence + the Machine) and Ethan Johns (Kings of Leon). For the new album, he is collaborating with Greg Kurstin, an American songwriter and producer who has worked with Pink, Beck, Kelly Clarkson and most notably Adele.

Yet even after all his achievements, McCartney is worried about the possible perception that he’s just grabbing “the man of the moment”.

He points out he worked with Kurstin two years ago after being told by mutual friends that he and the producer would get on.

“I was thinking that people who didn’t know I’d already worked with him might think, ‘Oh, he’s going with Adele’s producer, thinking he’ll turn him into Adele.’”

Does McCartney really worry about what a noisy minority might think?

“I don’t worry about it, but you’re conscious of it. There are some people I know who really don’t care what anyone thinks. I admire that. But most people I know aren’t like that.

“Even if it’s an ordinary job, you want to do it well, you want your work mates to think you’re cool, you want your boss to think you do a great job. It’s a common thing. So yeah, I’m like that. I’d prefer it if people like it.

“I probably have a bit of a hard time when people don’t like something I’ve spent a lot of time on. Making an album is sometimes like sitting an exam — learning everything and putting all the work in. And suddenly someone marks it. At that moment, most people hope they got it right. And that’s what it would be like for me: I’d put a record out and expect some bad criticism from some people, probably, but I kinda like it if people like what I’m doing.”

When you’ve released as many albums as McCartney has, there’s bound to be a milestone almost every year.

This year marks the 50th anniversary of Sgt. Pepper’s Lonely Hearts Club Band — the 32 million-selling record many believe was the blueprint for concept albums.

Remixed by Giles Martin (son of late Beatles producer George Martin) and with never-before-heard studio outtakes, the album returned to No. 1 on the UK charts in June.

“It’s amazing,” Paul says.

“It’s a good thing to have it released as an anniversary thing, but for people to like it and send it to No. 1 was unbelievable.”

Like many albums McCartney has been involved with, Sgt. Pepper’s has been passed down from generation to generation — a video of school children singing ‘When I’m 64’ became a feel-good internet moment last month.

“There was a time when it was pretty much just [people] your age that came to the show,” he says.

“Those people then grew up as we did; they had kids like we did. You’d see their kids coming to shows. Now we’re at the age where their kids’ kids are coming. You get the parents, their kids and the grandkids.

“I love that. I love that they can all come to the same show and enjoy it for different reasons. The kids are coming, presumably, because they like the songs, the parents are coming because of the nostalgia and what it reminds them of … it’s really nice.

“You see a lot of humanistic scenarios in the audience — people crying, laughing, singing along. The fact that the music can bring a whole family together is pretty cool.”

McCartney’s whole family now stretches to five children and eight grandchildren.

Daughter Mary followed her late mother Linda into photography — she shot her father in his London home for today’s cover of Stellar.

“She knows how to make you look good,” McCartney says of the never-seen-before images.

“Of course, instead of it being just anyone, it’s my little Mary. Well, she was my little baby, now she’s a hard-working mum with four kids. She’s a really good photographer. She can boss me around: ‘Don’t do that, stop, stand up, gimme a smile.’ She’s my favourite photographer.”

Paul and Linda had four children: artist Heather, 54, photographer and cookery writer Mary, 47, fashion designer Stella, 45, and musician James, 39.

The singer’s six-year marriage to model and activist Heather Mills ended badly (it’s his only no-go area when being interviewed), but resulted in his youngest child, 13-year-old Beatrice.

McCartney wed New Yorker Nancy Shevell in 2011; they’ll celebrate 10 years since their first meeting by travelling together to Australia for his tour.

While McCartney tops every “wealthiest musician” list, Shevell, 57, is no slouch herself, maintaining a nine-figure family transport fortune.

“Nancy’s very impressive. She is a businesswoman, she still runs her dad’s trucking company with 4000 trucks,” McCartney says proudly.

“She’s a trucker. She’s used to men’s humour. She’s a beautiful, smart and funny girl. She loves music … We’re very happy together.”

Most of McCartney’s children have adopted the vegetarian diet and animal rights beliefs that Paul and Linda were celebrity pioneers of back in 1975.

“We were on a farm, it was lambing season, and we were eating lamb. It suddenly clicked, ‘Maybe we don’t want to eat this anymore?’” McCartney recalls.

“It’s a style of life that I like and it’s always done me good … and a bunch of animals good, too.”

Aside from music, vegetarianism is one of the McCartneys’ major legacies; a chain of meat-free food options still bears Linda’s name.

“Most people are animal lovers,” he says.

“When you go vegie you become more aware of animal cruelty. Linda was very cool with it; she’d talk in a way that didn’t put your back up and she’d persuade you that these animals should be saved. She had such a good way about her that people would accept it, rather than getting into a big argument.

“We were able to do a lot of animal rights work — you feel good about that. I live on a sheep farm and the sheep die of old age. That never happens — they never reach that age, but my old lot do. It’s a nice feeling.

“We share this beautiful planet with all these other creatures. My idea is, why not give them their shot? Then you get the environmental angle which is very important these days, particularly when you’ve got someone like Trump who thinks it’s a hoax.”

Last year, McCartney copped flak from his Republican-leaning US fans when he was photographed with Hillary Clinton. As someone who divides his time between the UK and US, he doesn’t mince words when asked about Donald Trump.

“I’m not a fan at all,” McCartney says.

“He’s unleashed a kind of violent prejudice that is sometimes latent among people. Most people don’t feel it’s OK to be like that. When there were protesters at his rallies, Trump would say, ‘Oh beat them up, give them a good punch’ — wait a minute, I’m not sure that’s cool for a leader of a country to be saying that. Maybe for a hockey player.

“He’s unleashed the ugly side of America. People feel like they have got a free pass to be, if not violent, at least antagonistic towards people of a different colour or a different race. I think we all thought we’d got past that a long time ago.”

At 75, Paul is two years younger than the other remaining Beatle, Ringo, and just over a year older than The Rolling Stones’ Mick Jagger and Keith Richards.

“When I was a kid I’d look at someone who was 75 and think, ‘Bloody hell, that’s old,’” he laughs.

“But you get to 40 and you think, ‘40, that’s old.’ Then you get to 50 and think, ‘Well, 40 wasn’t so old.’ As you go on you look at the decade before and think, ‘I thought I was old then, but I wasn’t.’ Now you look at people the decade ahead of you and think, ‘Well, he’s still pretty cool.’

“I enjoy very much what I do: I feel healthy, I’m having a good time, making a new record, going on tour. It’s my dream come true. It’s what I always wanted to do when I was a kid. I’m still allowed to do it, so I’m not complaining.

“I belong to the group who think age is just a number. As you get to my age you’re inevitably aware of your mortality and you start thinking, ‘What does that mean to my kids and my grandchildren?’ But I’ve always taken the same attitude: when my time is up, that’s it. Until then, I’m going to have a laugh.”