15th wedding anniversary: The secret to Charles and Camilla's lasting marriage

The Duchess of Cornwall and Prince of Wales, pictured on their 15th wedding anniversary. Photo / Instagram

At first glance, it is the sort of photo families across the land might be exchanging via Whatsapp: the self-isolating grandparents beaming with their dogs, dressed casually, enjoying their daily breath of fresh air. They look cosy and happy in one another's company. And as they celebrate 15 years of marriage, nothing could sum up the Prince of Wales and Duchess of Cornwall better.

The royal couple, who have spent the past two weeks isolating separately in their Scottish house after Charles caught coronavirus, have been reunited just in time for their wedding anniversary. The official photograph to mark the milestone, taken by a member of staff in Birkhall's porch, shows them in full off-duty mode: one in jeans, the other in cords, cuddling Jack Russells Beth and Bluebell. They lean in slightly, fond but no need to put on a show.

It wasn't always this simple. For a new generation, too young to have known Princess Diana, the story of Charles and Camilla is one of true love thwarted by duty but rekindled in later life. It is easy to forget that, even 15 years ago as they tied the knot at the Windsor Guildhall, theirs was not a union universally celebrated in Britain.

"It seems ridiculous now that they wouldn't get married, but in 2005, it was a shock," says Robert Jobson, author of Charles: Our Future King and the journalist who broke the news of their engagement. "Everyone seemed to assume they were going to go on the way they had been – as partners. It was quite a moment really."

Public opinion did shift. The visible support of the Queen at the wedding was key, along with the bride and groom acknowledging their previous sins during the blessing. A few Diana fans brandishing banners on the day were largely forgotten.

"When they came out on the steps of St George's Chapel, she looked immaculate and people saw how happy they were – how genuinely happy he was," Jobson says. "Almost overnight, there was an acceptance of it. People thought, 'It's a new era'."

By then, their relationship had already been the subject of a slick PR masterplan, ensuring Camilla was at first palatable to the nation and then liked. Still, it was not an easy ride. Accusations of laziness – since proven without doubt to have been unfair – lingered, along with unflattering nicknames and an apocryphal but then all-too-believable story about being pelted by bread rolls in a supermarket.

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Thank you for all the well wishes on Their Royal Highnesses’ 15th wedding anniversary! 🎉 . 📷 PA / Clarence House 🎥 PA

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Clarence House was careful to spell out that the Duchess of Cornwall would not use the title of Princess of Wales, as she could have done, and would one day be Princess Consort rather than Queen. Undaunted, she took on causes close to her heart, got her head down, and slowly but surely made friends everywhere that mattered.

"People forget they had a very rough time," said Gyles Brandreth, the couple's biographer. "There has been a transformation. She's just terribly good, and it's sweet to see how doting he is. He's full of pride when he's talking about her."

Most importantly, their marriage has shown no signs of faltering. In public, they seem a genuinely good fit, unselfconscious and affectionate, with the ability to make those around them feel at ease. In private, friends say their shared sense of humour keeps them close, with an understanding over their distinct working and family lives letting them rub along comfortably even when in different houses. At work, the Prince and Duchess balance one another out: he the more earnest with a love of heartfelt speeches; she also serious about her work, but with a light touch.

On overseas tours, they boost one another through long days, and work the crowds as a team. In tactful asides to their "darling", one will remind the other of the time to keep the tight schedule on track. To the delight of photographers, they egg each other on for sometimes hilarious pictures with naughty animals, misshapen vegetables or novelty sunglasses. Charles has been known to bring the house down by referring to his "mehbooba" (or darling) in Urdu.

Nowadays, they have an air of being in on the joke. The Duchess can occasionally be caught rolling her eyes or winking at the press. One can easily imagine them in private, him in full flow about the environment as she smiles and nods. Those who have observed their relationship say Camilla has been a confidence boost and a calm influence.

"He's certainly more relaxed in her presence," says Jobson. "They can giggle away together at the same things."

"They're a great double act," adds one who has worked with them. "She gets him round a room in time. She puts a spring in his step and a twinkle in his eye."

In 2020, few would begrudge Charles and Camilla their lasting happiness. This year, the duration of their marriage will overtake that of Charles and Diana. As Britain has changed, so have its royals, and many blended families will recognise the success of a second marriage, with children and grandchildren existing happily on either side.

"The genius of the Royal family is that they reflect the world we now live in." says Brandreth. "The Prince of Wales and Duchess of Cornwall reflect their generation."

In some interviews, the couple have not been shy in sharing the secrets to their happiness. "It's always marvellous to have somebody you feel understands and wants to encourage," Charles has said. "Although she certainly pokes fun if I get too serious about things. And all that helps."

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The Prince of Wales and The Duchess of Cornwall will jointly visit the Republic of Cyprus and Jordan next month. Prior to this, The Prince will also visit Bosnia and Herzegovina. Key themes of the Spring Tour 2020 ⬇️ . 🇧🇦In the year of the 25th anniversary of the genocide, The Prince will visit Bosnia and Herzegovina where he will highlight reforms to improve citizens’ lives. 🇨🇾The Prince and The Duchess will make their first official visit to The Republic of Cyprus to recognise the work of the UN Peacekeeping Force and celebrate traditional Cypriot culture. 🇯🇴Their Royal Highnesses will visit The Hashemite Kingdom of Jordan to learn what the country is doing to support refugees and showcase its rich cultural history. Read more about Their Royal Highnesses’ forthcoming Spring Tour, which will take place from 17th to 25th March, by following the link in our bio. 📸 PA

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"He's incredibly kind," she has said of him. "He has got a very good sense of humour. And, of course, he's wonderful with children. My grandchildren adore him, and they can't wait to see him."

Yet, even within earshot of journalists, Camilla makes no secret of her wifely frustration for his work ethic, once joking she may have to hold up a sign to get his attention while he was on the go. Once asked how they would spend his birthday, she ventured that it would be "bliss" to sit still and enjoy the sun together, explaining, he's "not one for chilling."

Fortunately for the Duchess, that modest dream may come true today. With coronavirus comes – even for the heir to the throne – a measure of enforced relaxation, and no better place than Birkhall to enjoy it.

Out of self-isolation, the couple will be able to walk in the garden undisturbed, taking in the landscape he loves. With a reduced domestic staff at the house, there will still be tea together and a home-cooked dinner to follow. They will swap cards, likely based around their in-jokes, and gifts – should the post be delivered on time. For an extraordinary couple, who have been known to call one another by the alter egos of Fred and Gladys, it will be an ordinary, quietly happy day.

"They are rock solid," said a friend. "Their marriage is the foundation upon which everything else in their lives sits."

Neither those around them, nor the public that has watched from afar will have any doubt there will be another 15 years to come and counting.