On this day – how sensational photos of Princess Margaret in a swimsuit prompted the Queen to call her a 'GUTTERSNIPE'. And an enduring romance that changed royal weddings forever…

When the photos finally surfaced, the entire country was shocked, if not the friends who were privy to the secret.

The apparently happily married Princess Margaret, in a skin-tight swimsuit and corset, lies close to a penniless boy toy 18 years her junior.

He is carrying a pair of Union Jack parakeet smugglers that she bought for him within minutes of their first meeting.

This is February 1976. And she, in the 15th year of her marriage, is hopelessly in love.

Her sister, Queen Elizabeth II, knows all about it – and makes it known that she disapproves of Margaret's 'gutter snipe life'.

But their love affair survived a divorce, a nervous breakdown and a suicide attempt. It lasted seven long years and changed the face of royal weddings forever.

Roddy Llewellyn, a lowly pen pusher at the College of Heralds, was the man who made Princess Margaret happier than ever before.

The princess was once second in line to the throne.

With her signature hourglass figure and permanent cigarette holder, she was a sexy, headstrong, dangerous and imperious beauty.

Her 1960 marriage to bohemian photographer Tony Armstrong-Jones seemed to go the hip way after her clandestine relationship with war hero Group Captain Peter Townsend collapsed in scandal and accusations.

More than twelve years later, however, the wheels fell off.

Tony – who was given the title Lord Snowdon as a wedding present – ​​was serially unfaithful from the start. Margaret tried out a few lovers in retaliation.

But it wasn't until she was invited by her lady-in-waiting, Lady Glenconner, to lunch at the family home in Scotland in August 1973, where she sat next to a floppy-haired 25-year-old, that the 43-year-old princess truly fell in love.

It took less than a minute. It was crazy.

“He was fascinated by this refined, voluptuous woman, so funny and so easy to talk to,” wrote the eminent biographer Anne de Courcy.

'As she made it clear [from the very first moment] how attracted she felt to him.”

Fascinatingly, the age difference in the romance mirrored Margaret's infamous affair with Peter Townsend – while he was 16 years older than her, she was 18 years older than Llewellyn.

Roddy, Margaret's intimates said, was tender and kind in a way Snowdon could never be.

On the other hand, he didn't have the stamina of the older man in the bedroom.

Even as their marriage fell apart, Snowdon strode naked down the hallway dividing their bedrooms and stood imposingly before his wife.

“He threw open my bedroom door, stood there with no clothes on and then… what could I do?” Margaret later told a friend.

It was Snowdon's sexual dominance that caused Margaret to submit to him in other aspects of her life, Ms De Courcy claims.

It wasn't the same with Roddy. Young, kind and thoughtful – the exact opposite of Snowdon – he began to hesitate about Margaret's sexual demands after the initial honeymoon period was over.

“He had never had a long-term relationship with a woman,” Ms. de Courcy explained. “Now he was in a relationship with someone who was not only much richer and older, but also had a demanding, intense and possessive personality.”

According to Roddy's older brother Dai, the physical side of the relationship proved very difficult to maintain.

But there is no doubt that they loved each other. And three years into the relationship – still, surprisingly, a closely guarded secret – the couple flew to the hideaway island of Mustique as 'Mr and Mrs Brown'.

They enjoyed the exotic life on the small Caribbean island and could pretend they were really married – safe in the knowledge that prying eyes and long-lens cameras were unlikely to intrude on their privacy.

They were wrong.

Someone took a photo of them, silhouetted against the backdrop of the ocean, clearly a loving couple oblivious to the rest of the world.

The photo appeared in a British redtop newspaper a few days later.

All hell broke loose. To the British public, Margaret and her husband – plus their two small children David and Sarah – were a close-knit unit, living examples of the idea of ​​a royal family.

Over the course of the day it caused as big a scandal as the Townsend affair – and the publication of the photo around the world caused Snowdon to demand a divorce.

He had played the game, he argued, by keeping his extramarital affairs secret. However, if Margaret didn't care who knew about her and Roddy, he would have left.

At the time, the Queen's former private secretary, Lord Charteris, made it known that the sovereign believed Margaret was living a 'gutter snipe life'.

This was an extraordinary – some historians would say unique – insight into the relationship between Lilibet and her sister.

Unable to cope with the pressure of publicity, Roddy ran away – first to the Channel Islands, then to Turkey and then to South America.

While traveling on the bus, he informed a fellow passenger that he had “had an affair with a married lady and it was all too much for him and sex had become a problem.”

Margaret, deprived of the company of both her husband and her lover, fell into a downward spiral and took an overdose of Mogadon sleeping tablets.

Her recovery was weak, cranky and long.

Eventually the lovers reunited. But Roddy, having escaped the claustrophobic atmosphere of the relationship, was looking for a new life – and found one as a successful landscaper, author and TV presenter.

He inherited the family baronetcy – he is now Sir Roderic Llewellyn – and married Tania Soskin, the daughter of a film producer, to great effect.

These may not have been the last words they shared, but they show how a passionate affair between two people from vastly different backgrounds and ages can easily go wrong:

Princess Margaret (modeling a frothy pink dress that shows off her curvy figure): “What do you think, Roddy?”

Llewellyn: 'You look like a strawberry ice cream cone.'