On a sunny spring day not long ago, a friend of mine clocked Andrew Parker Bowles in South Kensington. The ex-husband of the Queen was smartly turned out in a terrible coat, the sort that country gentlemen and the King like to wear. He was striding purposefully past the Tube station and had a twinkle in his eye.

“You know Hugh Grant’s opening scene in Bridget Jones,” my friend told me later, “when the lift doors open and his eyes dart left and right? And you know, right there, that this man is a charming disaster who’ll show you a good time? That was him.”

Parker Bowles is 83 now and apparently still, even in passing, irresistible. Nearly 60 years after he met Camilla Shand, 28 years since they divorced and 18 since she married the King, he remains a vital sounding board for the new Queen.

“Everyone loves Andrew,” the Marchioness of Lansdowne, a close friend of Camilla’s, told Roya Nikkhah, Sunday Times royal editor. “He’s a real charmer, but he’s always terribly misbehaving. Andrew will ring her up and tell her when she’s got something wrong and she’ll ring him up and say when he’s misbehaving.”

The Parker Bowleses on their wedding day, July 4, 1973.

She was 18 and he was 27 when they met at a party in 1966. Legend has it that she arrived at the party with one boyfriend and left with another – him. What no one disputes is that from the start, theirs was a tempestuous courtship and, eventually, marriage. A friend painted a portrait for Rebecca Tyrrel for her book Camilla: An Intimate Portrait, of how they spent weekends at his bachelor pad in Notting Hill. If you popped round on a Saturday morning, the friend said, “Andrew would be up and about cooking breakfast and making coffee. Around 11, Camilla would stagger down looking a little disheveled, wearing one of his big shirts. She would sit on Andrew’s knee and tease his hair. They clearly had a very lusty, healthy life together.” Another said that “his greatest gift to women was the knowledge that sexuality was healthy”.

Camilla the vivacious deb was smitten with the dashing lieutenant in the Household Cavalry. They dated on and off for seven years and he was serially, cheerfully, reliably unfaithful throughout. Caroline Graham’s 2001 biography of Camilla relates how she once turned up at his flat unannounced and he opened the door in his pants. “Who the hell have you got in there?” she shouted. “Which tart was it last night?” The tart in question was ejected, red-faced and struggling with her bra.

Another story has Camilla letting down the tires of his car when she spotted it parked outside one of her girlfriends’ places and daubing what she thought of him on the windscreen in pink lipstick. An ex told Tina Brown in her book The Palace Papers that Parker Bowles’ power over women was “extraordinary. Women had no hesitation believing what he said. He seemed to compel them into loving him, although he sometimes dropped them so quickly their heads span. He could be completely ruthless in that sense.”

Parker Bowles is 83 now and apparently still, even in passing, irresistible.

He was born just after Christmas 1939, the eldest of four children to Ann, commissioner of the Girl Guides whose nickname was Rhino, and Derek, a former army officer of aristocratic descent and friend of the Queen Mother. The National Portrait Gallery has in its collection a photograph of the young Andrew, a look of mischief on his face, taken in 1947 with his mother and two siblings. Brought up a Roman Catholic, he was educated at Ampleforth and at 13 served as a page at the Queen’s coronation.

Parker Bowles plays polo in Kenya, 1971.

He went to Sandhurst and was commissioned into the Royal Horse Guards in 1960. As he rose through the ranks, he pursued a parallel career as a keen amateur jockey, making his debut on a one-eyed hurdler called Gorse Bird. He broke his back falling off a horse at Ascot. He has the stitches preserved in a jar and displayed on a shelf at his Cotswolds home. Two years later, in 1969, he rode in the Grand National.

At 27, he was disinclined to settle down when he met Camilla. One of his girlfriends, Lady Caroline Percy, reminisced, “There were always other girls.” When Camilla cornered her at a party, Percy lost patience. “You can have him back when I’ve finished with him,” she snapped.

Eventually, having watched his daughter being messed around for seven years, Camilla’s father took command of the situation. He bounced Andrew into proposing by announcing their engagement in The Times. (Years later, the redoubtable Major Bruce Shand MC, then aged 88, bounced the King into marrying her as well, by insisting Charles make an honest woman of her before he died.) The proposal left Camilla walking round “with stars in her eyes – the cat that got the cream”. It left Prince Charles, with whom Camilla had dallied, bereft. Some say that the dalliance began as a way to make Andrew jealous.

After a rowdy stag night at White’s in July 1973, Parker Bowles promised faithfully and untruthfully to forsake all others, in front of 800 guests at the Guards’ Chapel in St James’s Park. It was the society wedding of the year, attended by the Queen Mother and also Princess Anne, one of his exes, who was said to be “in pieces” about it. The reception was at St James’s Palace, where Princess Margaret put in an appearance.

Around 11, Camilla would stagger down looking a little disheveled, wearing one of his big shirts.

The couple honeymooned in the South of France and moved into Bolehyde Manor in Wiltshire, which the gossip columnist Nigel Dempster described as a “splendid mansion”. Their first child, Tom, was born the following year and their daughter, Laura, four years later. Tom’s godfather is the King, an honor which his father is said to have relished.

Faced with her husband’s serial infidelity, Camilla, argues Tina Brown, kept alive the contact with Charles, and the sexual charge between them, as a sort of insurance policy, finding comfort in Charles’s devotion. In return, she personally vetted all his girlfriends as potential wives. In 1980, Charles spent two weekends with Lady Diana Spencer at Bolehyde and proposed in its garden.

Parker Bowles progressed through the ranks, reaching that of major in 1971 and serving in Northern Ireland, and later as aide de camp to Lord Soames, the father of one of his exes and the last governor of Southern Rhodesia before independence. When Prince Charles arrived in 1980 for the country’s independence celebrations, Parker Bowles checked over the royal itinerary, which included a ride on a buffalo called Ziggy. Concerned for the safety of the heir to the throne, Parker Bowles took Ziggy on a test drive and was promptly thrown and gored. He was taken to hospital and Ziggy was expunged from the record.

Parker Bowles, right, with Princess Diana in 1981, just ahead of her marriage to Charles.

Back home, and by now commanding officer of the Household Cavalry Mounted Regiment, in 1982 he was in charge when the IRA detonated a nail bomb in Hyde Park as his men rode past.

In the early Eighties, he was contacted by the artist Lucian Freud. They struck up a close friendship based on a love of horses, racing and art. They galloped round Hyde Park and visited Freud’s bookie in Ireland and the National Portrait Gallery in London after hours. Freud painted a portrait of Parker Bowles, which the subject glimpsed while it was a work in progress. When he complained that he looked fat, Freud added another inch to his stomach to shut him up, as Parker Bowles put it. He didn’t buy the painting, he later told Tatler, because he didn’t have a spare $4 million lying around and “a 7ft picture of myself looking rather red-faced and fat wasn’t my idea of fun”. The Brigadier later sold for $34 million at Christie’s.

While his wife went hunting with Prince Charles, Parker Bowles played on the prince’s polo team, became a member of the Jockey Club and a bigwig at racecourses. He escorted the Queen Mother round the Cheltenham Festival every year, and hosted her at Bolehyde and later at Middlewick House, where he and Camilla moved in 1986. In return, the Queen Mother invited him and Camilla every year to stay at Birkhall, the house which is now Charles and Camilla’s base in Scotland.

Lucian Freud’s The Brigadier, a portrait of Parker Bowles, went to auction at Christie’s in London in 2015.

In his private life, he had reached an arrangement of sorts with his wife. He commuted to London during the week to pursue his career and leggy Sloane Rangers. She remained in the country, bringing up their children and resuming her relationship with Charles. It was, a family friend said, “a very English marriage. You just bite the bullet and keep going. Camilla was terribly loyal. He would have the ladies and she would have a nice joint of beef on the table. That generation had a whole different code. Nobody ratted on anybody else.”

One exception was Lord Charteris, private secretary and confidant of the Queen, who informed her that her eldest son was sleeping with the wife of a Household Cavalry officer “and the regiment doesn’t like it”. Nor did the Queen, who gave instructions that Camilla was never to be invited to any formal event at which she would be present. When the royal family held a lavish ball in 2000 to celebrate the 100th birthday of the Queen Mother, the 70th of Princess Margaret, 50th of Anne, 40th of the Duke of York and 18th of Prince William, Parker Bowles was invited with his second wife, but Camilla was not. (They were also invited to Charles and Camilla’s wedding, allegedly at the Queen’s behest. Some said the invitation was a reward for his never having spoken publicly about his ex-wife or her relationship with Charles.)

As the marriage became a game of musical beds, the code of loyalty in their social circle ran deep. Two months after the publication of the Camillagate tapes of an intimate phone call between Charles and Camilla, an old flatmate of Andrew’s gamely popped up to say, “Andrew says his wife has never slept with Charles and I believe him.”

“A 7ft picture of myself looking rather red-faced and fat wasn’t my idea of fun.”

As the scandal deepened with the publication of Andrew Morton’s book Diana: Her True Story, laying bare Camilla’s involvement in Charles’s marriage, any suggestion that the Parker Bowleses might divorce was dismissed. The idea was, said Andrew’s cousin Lord Beaverbrook, “preposterous. Anyone who knows Andrew will understand that he will stand by his wife.”

Camilla Parker Bowles and Prince Charles attend the Mey Highland Games in 2003, two years before they married.

“They will never divorce,” said Andrew’s brother, Simon, “and while the relationship is rather eccentric, it appears to work. They get on well.” Tina Brown, who met the couple at their home in 1981, described their dynamic as “a kind of electric indifference” and said that Andrew was “amused and flattered” that Charles was in love with his wife. The Parker Bowleses continued to socialize together in public, but in private they largely went their separate ways. Charles would visit Middlewick, an 18th-century manor set in 500 acres, when Andrew and the children were elsewhere. But another loyal friend described theirs as “a rock-solid partnership. Dynamite couldn’t blow them apart.”

In the end, it wasn’t dynamite that blew them apart, but Charles. The Parker Bowles marriage had batted on through Camillagate and the Morton book, and Andrew appeared to have taken both on the chin. “Andrew is so loyal to the Crown,” joked Lord Soames, “that he is prepared to lay down his wife for the sake of his country.” But Charles’s admission of adultery in an interview on television was the last straw. According to the Times royal correspondent, Valentine Low, the Dimbleby interview led directly to Parker Bowles filing for divorce in 1995 after 22 years of marriage. He was 56, Camilla 47.

“The decision to end our marriage was taken jointly and is a private matter,” they said in a statement, “but as we have no expectation that our privacy will be respected, we issue this in the hope that it will ensure that our family and friends are saved from harassment… Throughout our marriage we have always tended to follow rather different interests, but in recent years we have led completely separate lives.”

Parker Bowles and Camilla, then the Duchess of Cornwall, attend the wedding of their daughter, in 2006.

They had in fact been separated for three years. By the time the press arrived at Middlewick, Camilla was at Highgrove and Andrew was in a townhouse in Malmesbury with his mistress, Rosemary Pitman, whom he married the following year. The couple regularly hosted Charles and Camilla for weekends, were guests at Sandringham and went to the royal wedding in 2005, where Andrew was said to have behaved like the mother of the bride. When Pitman died in 2010, Camilla was said to be “deeply saddened”.

Today, Parker Bowles lives out his retirement in the Cotswolds in a house full of memorabilia, surrounded by a garden with neat rows of vegetables. Duchess of Cornwall roses bloom in the flower beds, a joke present from his ex-wife – the Duchess of Cornwall. He is chairman of a property development company, but joked recently that “nobody listens to me”. The company is redeveloping an old military hospital in Hampshire, which it is hoped the King will open later this year. He has, Parker Bowles said genially, already expressed a view on the design. “He had strong opinions on the windows. Let’s just say they weren’t exactly how he wanted them.”

Parker Bowles and Princess Anne at the Cheltenham Races in 1997, two years after he and Camilla divorced.

Thoroughly enmeshed in the royal world of his first wife, he represented her last October at a funeral and has represented his old flame, Princess Anne, on several occasions (and is godfather to her daughter, Zara). A friend described him as someone “from a bygone age – an old-fashioned soldier for whom honor is everything”. Talking about the antics of the Parker Bowleses’ Gloucestershire set in the Eighties, the novelist Jilly Cooper once remarked, “I bet Worcestershire is just as degenerate. Horses always lead to these things.” As for Andrew, asked about Cooper’s admission that he was an inspiration for her upper-class cads, he replied, “I took it, and continue to take it, as a great compliment.”

Hilary Rose is a longtime columnist for The Times of London and the author of the weekly column How to Get Dressed