Family lore’s a great thing. I was raised on tales of the ancestor who galloped home carrying news of the victory at Waterloo and of the great-uncle, a Seaforth Highlander, left behind at Dunkirk but shepherded to safety through France thanks to the efforts of Church of Scotland minister Donald Caskie, the so-called Tartan Pimpernel.

When she met the 23-year-old Prince of Wales at a party in 1972, the young woman born Camilla Rosemary Shand wheeled out a winning ancestral anecdote of her own: “My great-grandmother was the mistress of your great-great-grandfather,” she said. “I feel we have something in common.”

As chat up lines go, it’s a zinger.

That mistress, by the way, was society hostess and upper echelons It Girl Alice Keppel. Born into the (faintly) aristocratic Edmondstone family, she was raised in Duntreath Castle in Stirlingshire and in later life became the long-time lover of Edward VII, the original ‘Playboy Prince’. Smart, sassy and beautiful (at least if the photographs and portraits are to be believed), she died two months after Camilla Shand was born.

Fast forward 50 years and the 23-year-old prince is now a 73-year-old monarch, King Charles III. Alice Keppel’s great-granddaughter is now Camilla, Queen Consort, having married the then-Prince Charles in April 2005. From a risqué comment over the canapes she has travelled to the heart of the British establishment and to the foot of the throne itself. It’s the kind of story you could imagine being turned into a film, a mash-up of every will-they-won’t-they rom-com from Four Weddings And A Funeral and When Harry Met Sally to A Castle For Christmas, last year’s much-maligned, Scottish-set Netflix flop starring Brooke Shields and Cary Elwes.

In other words it’s a great love story. It has a wonderful opening, a turbulent middle act (more on that later), and a resolution which is, quite literally, the stuff of fairy tales. It adds up to a narrative arc so neat and perfect and colourful it’s like a big, neon, party rainbow. Their fates really were entwined.

Dig deeper into the life and personality of the Queen Consort and there’s plenty to like. Although plush and Grade II listed, her childhood home in Sussex was not vast or gaudy or colonnaded or any of that stuff. It looks like one of those places Google throws up when you search on ‘gastro-pub + country hotel’. Later it became the home of actor James Wilby, who sold it in 2015 for £2.5 million. Sure, it has a tennis court, a swimming pool and an orangery, whatever that is. But it’s hardly Brideshead.

American journalist Sally Bedell Smith, who has written for Vanity Fair and the New York Times among other august publications, penned a biography of the then-Prince Charles in 2017. She clearly liked what she found where his wife was concerned.

“During her 20s, Camilla Shand was considered quite a catch,” she writes at one point. “Along with an upper-class pedigree, she had fine features, a low husky voice, merry deep-blue eyes and a fetching figure with a large bust.”

There’s more. Her childhood? “Blissful”. That Grade II listed childhood home? “Rambling … rows of gumboots stood to attention by the door.” Her personality? “[A]n extrovert tomboy, who was mad about ponies and horses … When she was just nine, her father Bruce had introduced her to foxhunting. She took instantly to the thrill of the chase, vaulting the fences with courage and vigour.” Education? “Sketchy” is Bedell Smith’s polite description, though she made up for it in other ways. “Having left school with just one O-level, she’d gone on to a Swiss finishing school to learn how to roast a chicken and lay a table correctly.”

In the person of Camilla, she says in summation, “the Prince found not only a sympathetic ear but also warmth, vivacity and a goofy sense of humour … For a young Prince with downbeat tendencies, that sort of personality was catnip.”

Today, catnip undersells it. In even the most sombre moments of what has been a sombre 10 days since the death of Queen Elizabeth II – during even the stiffest and most formal ceremonial events – the bond between husband and wife has been clear. On more than one occasion, it has been stated verbally. “I count on the loving help of my darling wife Camilla,” said the King on September 9 in his first televised address to the nation, the day after the death of his mother was announced. Another day on, in his speech to the Accession Council at the proclamation ceremony in St James’s Palace in London, he had more words on the subject. “In all this, I am profoundly encouraged by the constant support of my beloved wife,” he said. By ‘all this’ he meant explicitly the taking up of his new responsibilities as sovereign and the discharge of those duties. But by ‘all this’ he meant so much more besides.

At 25, standing in front of the heir to the throne, Camilla Shand was right. They did have something in common. They still do.

But there’s a parallel strand to the story and a darker side. Whether or not you believe there were external forces keeping them apart, they both chose to set their lives on very different tracks by marrying other people when they should have married each other. Enter Diana, Princess of Wales. And enter the rest of the world with her because it was she who turned the British monarchy from a relatively parochial concern into one which could command both the front page of Vogue and the mass market magazines and tabloids on which the denizens of convenience store America once loved to snack.

In this tale there’s another Camilla, one who is not goofy or merry or fun. In this tale she is the Other Woman, a sort of Lady Macbeth figure once nicknamed ‘the Rottweiler’ by her rival. A figure much briefed against.

In a soundbite which become first famous and then notorious, Diana described her marriage as having three people in it. She wasn’t wrong. Some royal biographers date the re-kindling of Camilla’s relationship with Prince Charles to 1980, before he married Diana, but it was certainly a fact by December 1989 when an intimate telephone call between the lovers was recorded. A transcript was later published in The People newspaper in January 1993 and the affair became known as Camillagate. You know you’re in trouble when you have the suffix -gate added to your name. A year earlier Andrew Motion’s book Diana: Her True Story had laid out the extent of that relationship and the stress it had placed on the royal marriage. We now know it was written with the full co-operation of the Princess of Wales.

Since her death in 1997 things have become even more difficult as Diana is parlayed into a sort of modern-day saint. Candle In The Wind, the Elton John song written about Marilyn Monroe and the icon she became, is now associated just as much with her as with the doomed star of Some Like It Hot. As a result Diana has assumed much of Marilyn’s tragic glamour. The two women have become conflated in the public imagination, tangled up together. It makes for a powerful mix.

It doesn’t stop, either. Filming has just resumed on The Crown, Netflix’s award-winning dramatisation of the Royal family’s eventful history, and wouldn’t you know it they’re up to the bit where Diana visits Bosnia in 1997, just days before her death in Paris. Cool, willowy, ballerina-turned-actress Elizabeth Debicki plays the Princess. Last year, meanwhile, Oscar-winning Chilean director Pablo Larrain cast cool, willowy Kristen Stewart as Diana in Spencer, a biopic of sorts. Stewart, you will recall, is an actress beloved of Generation Z for her role as Bella Swan in the hugely influential Twilight movies. At a stroke, another layer was added to Diana’s pop culture mystique – and the greater that mystique becomes, the greater the scrutiny of the other players in the drama.

So in a sense there are still three people in the marriage, though it may be the Queen Consort who now has cause to muse gloomily on the fact. Then again, the fact is the UK’s head of state is happily married to a woman he has loved for decades. A woman with whom, as she once observed, he has much in common. Perhaps, at the end of the day, that’s all that really matters.