The couple, who have seven children between them – Paul, three adult daughters, and Diane, four adult children – got back together "a comparatively short time ago".
"And it was just so obvious that it would be a waste of our lives not to marry," Paul says.
As the pair settle into their chat with the Weekly, sipping takeaway coffee that Diane has just brought home "because we've got about 25 coffee machines that neither of us know how to use", it's impossible not to see how content they are.
They're happiest doing "old people stuff together", Paul reports, like watching TV or going out for a meal. But he is also thrilled that Diane shares his love of boating because two years ago Paul launched an 80ft yacht in honour of his late mum, Olive.
What they've also discovered through their many hours of talking is that "there have just been all of these symmetries between our lives", Paul says.
"We were both born in Auckland into dysfunctional families, to one degree or other – Diane's much more so than mine. And then both of us were taken overseas at approximately the same time. For me, it was to England, where I was brought up. She went to Australia.
"Often in conversations we'll realise that we had been watching the same thing on TV at the same time, or in the same place, or doing the same thing at exactly the same time. So what we share are the same reference points.
"And here's the other lovely thing," Paul adds. "We also give each other space to do the things that we enjoy separately. For instance, Diane has a beautiful apartment in London and she absolutely loves that. I love my house in Palm Springs. So we'll go to Palm Springs and spend a week there together, then she'll go on to London for a month and I might follow her over and spend a couple of weeks with her in London, then we'll fly back to New Zealand together.
"Diane always has interesting things to say when you ask her, 'What did you do today?', because we're both out and about doing bits and bobs."
The couple decided to marry during a conversation at home one evening.
"We were sitting down together and we started talking about our relationship," Diane reveals. "We decided that if we were going to be together, then we needed to make a real commitment to this because we've been together before, so this had to be big. You know, what's the biggest commitment you can make? It's marriage."
If Paul had had his way, the couple would have got hitched at a registry office. Diane's London home is not far from the Chelsea registry office and the couple have always taken delight in seeing newlyweds spilling out of the building.
"You'd see a hugely pregnant bride with 400 bridesmaids or a nervous-looking couple waiting outside. Paul always thought it would be amazing to just get married there and rip somebody off the street to take a photo and send it home to the kids," Diane laughs.
"But our children are the most important people in our lives, as well as our grandkids. I wanted to share it with them."
The couple made sure Paul's daughter Bella had her big day first. Bella married the love of her life, Julyan Collett, on March 6 in a Disney-themed celebration. Paul and Diane held their much more scaled-back ceremony the following weekend.
"Bella's wedding was the important wedding," Paul says. "This was not my first wedding and it wasn't for Diane either. So it was important for us to have close family around us and just have a lovely day – and it was perfect, absolutely gorgeous."
The couple's March 14 wedding day dawned crisp and clear. Diane booted Paul out of their Auckland home, then called in the caterers and florists, who got to work creating a wonderland.
The terrace was set out with two long tables for a shared meal, then the entire space filled with masses of flowers, including urns overflowing with roses in pink and cream.
"It was just beautiful," says Diane. "Paul had said, 'You're not having a lot of flowers and things like that, are you?' And I'd said, 'Yeah, yeah, yeah, don't worry.' Then Paul came home and said, 'I see you listened to me about not having a lot of fuss.'
"It was very different from what he probably would have wanted, but I loved the way he just embraced it. We had the most wonderful day."
When guests arrived, the couple greeted them in casual attire – Paul in a Boss shirt and Tommy Bahama pants, and Diane in a sundress she'd picked up in Capri, Italy. "Just imagine a summer picnic in the garden. That's what it was like," tells Diane.
After the happy couple had shared a meal with their guests, they changed into wedding wear. Paul added a Working Style jacket and Diane changed into a stunning calf-length white gown by Australian designer Dion Lee. They were married by Kiwi actor and marriage celebrant Simon Prast, exchanging traditional vows.
"There was this wonderful moment where Simon asked us to commit 'for richer, for poorer' and everybody laughed because we both come from very, very poor backgrounds, yet here we were in this fabulous setting, surrounded by our family and friends," says Diane.
In a nod to Paul's beloved late mum, Paul's daughter Lucy wore the same dress that Olive had worn to Paul and his first wife Rachael Hopes' wedding and "it really did feel like Mum was there", Paul says.
Rachael was also present. "It was important that Rachael was there," Paul explains, "because we've got three beautiful daughters together and she's part of the family."
In an ideal world, Paul and Diane would have set off afterward for a romantic honeymoon abroad, but New Zealand went into level four lockdown "so our honeymoon was a government-enforced lockdown in our house," Paul chuckles. "Thank God we get on well because that would have tested any marriage. But we're both homebodies and we just got on so well."
When lockdown ended in May, Paul set off for his Palm Springs home to finish his book. He'd been firing off chapters to his publicist as soon as he'd written them so he couldn't be tempted to rewrite them.
"Because this memoir is genuinely the first six months of 2020, so it really is written in real time," explains Paul. "I go back into my past to contextualise things, and you do find out a lot about me because it is brutally honest. But I don't give a s*** what people think because it's just me."
The result is a fun read with many twists and turns, as well as intriguing anecdotes about famous figures such as Helen Clark, Sam Hunt and Billy Connolly.
The most moving chapter is a deeply personal account of his final days with his dear mum, Olive. Paul was with her when she drew her last breath.
Paul's Palm Springs home is the setting in which the book both begins and ends. It's part of a nudist community and the place where Paul feels most at ease with the world.
The keen nudist admits it's not his wife's thing, "but when Diane or the girls come over they can keep their clothes on. There's no need for them to be naked. The only rule is they can't swim or lie by the pool unless they're naked.
"The first time I took [daughter] Lucy, she was literally there 10 minutes before she was naked in the pool drinking mimosas with my naked neighbours. But Bella thinks we're deviant freaks and Sophie, it's just not for her.
"Diane probably fits into the same category as Sophie. But she loves the people there and she's made some lovely friends. It doesn't matter to me because I don't want to convert anyone. It's just important that they enjoy the house."
The couple is also keen to hit the high seas as much as they can aboard Paul's yacht Olive. Smiling, Diane says, "We're both 60 now and this is our final chapter. We just want to spend it together."
