It was Christmas, 1995 and 100 or so colleagues were celebrating the end of the year at London's five-star Lanesborough Hotel.

The guests were all staff members of the Prince and Princess of Wales. Despite the fact the royal couple had separated three years earlier, they had maintained a joint office.

Now it was a chance for their equerries, secretaries and myriad of other support personnel to let their hair down. The mood was jubilant by all accounts and the drink was flowing.

What happened next was an incident that still lives on in royal infamy, and which dramatically put a spotlight on a simmering dislike Diana had been fermenting.

According to a number of reports from eyewitnesses who were there on the night, Diana strode towards one particular blonde female employee. When the royal got close, she said in a voice loud enough that others could hear, "So sorry to hear about the baby."

The woman, Tiggy Legge-Bourke — Princes William and Harry's beloved nanny — burst into tears and left the room.

The scene was perhaps one of the more disgraceful alleged episodes in the tawdry War of the Wales that dominated the global press for much of the '90s.

Tiggy might have ostensibly been a lowly nanny, but her innocuous title and paltry salary belied the central place she occupied in all three Princes' lives. For years, she had been a key source of steadfast emotional support and joy for Wills and Harry as their parents duked it out on the front pages of British tabloids and behind closed doors.

However, rumours about Tiggy's relationship with Charles had been brewing. Photos of the Prince of Wales greeting her with kisses on the cheek in public had only served to set tongues wagging with speculation of just how close the 40-something royal was to the woman he trusted to care for his sons.

While Tiggy left Charles' employ in 1999 when she married, this week she re-entered the spotlight after she was photographed attending Archie Harrison Mountbatten Windsor's highly secretive Windsor christening.

For decades since then, rumours of affairs, intriguing paparazzi photos and assassination fears have swirled around Tiggy: So just who is the woman who drove Diana so wild?

Right royal connections

It was early 1993 and Charles and Diana had recently, only months before, finally separated. While he had always been a doting father, entertaining two rambunctious boys when they were home from boarding school was a daunting prospect for a Prince who enjoyed discussing Tuscan architecture and spirituality.

Though not pictured in the official christening photo released by the Duke and Duchess of Sussex, Tiggy was spotted attending baby Archie's Christening. (Photo / Supplied)

Enter Alexandra "Tiggy" Legge-Bourke. (Her nickname came from Mrs Tiggywinkle, the Beatrix Potter character.)

Tiggy was a jovial woman who not only had the requisite experience — having worked at a Battersea nursery — but came replete with strong royal connections.

Her mother Shan was a lady-in-waiting to Princess Anne and her brother Harry was a page-of-honour to the Queen. She had attended the same Swiss finishing school as Diana (and Camilla, incidentally) and her step-grandfather was William Sidney, First Viscount De L'Isle, who was the Governor-General of Australia from 1961-1965.

She had also grown up within Charles' social orbit. He would regularly shoot on the Legge-Bourkes' Glanusk Estate in south Wales.

It was Lady Susan Hussey, Wills' godmother and a lady-in-waiting to the Queen, who suggested that Tiggy would be perfect for the role.

The then-29-year-old had already spent four years working in the royal household as an assistant to Charles's private secretary Commander Richard Aylard.

Shooting and fishing

By all accounts the young Princes took to her immediately. Her approach was very jolly: Hunting, shooting, fishing, days at the polo and go-karting, all the sort of dirty, joyful activities two upper-class lads might enjoy on the agenda.

"I give them what they need at this stage: fresh air, a rifle and a horse," Tiggy reportedly said of her approach.

Tiggy was, perhaps unkindly, given the nickname The Thumping Great Sloane.

Wills and Harry were huge fans of Tiggy. (Photo / Supplied)

She quickly became a central figure in the boys' life both at St James' Palace — where their father lived in London — and Highgrove, his vast Gloucestershire estate where they often spent weekends. "She was part servant, part sister and part mother," a former aide has said.

Soon, she was skiing with the Wales' in Switzerland, taking Harry on safari to Botswana and was on the sidelines with the young Princes when they watched their father play polo.

Tiggy became so close to her young charges that it wasn't long before she was referring to them as "my babies".

At one stage, Prince William disinvited both of his warring parents to a significant Eton event. Both were reportedly taken aback when they discovered he had invited Tiggy in their place.

Diana takes aim

There were many reasons that Diana disliked Tiggy. For starters, her young sons were clearly in love with the fun-loving woman who got to spend hours and hours with the young HRHs.

But while Wills and Harry were huge fans of this playful older sister-type figure, their mother was not.

Tiggy and the Princes on the Balmoral Estate in 1994. (Photo / Supplied)

Diana is said to have hated the fact that Tiggy smoked near her boys and during legal wrangling as part of Wales' divorce, the Princess sought official clarification of just what exactly Tiggy's job was and how involved she was in Wills and Harry's lives.

"On her instructions, I drafted letters from the Princess to her husband pointedly asking for clarification of Tiggy's duties and asking to be involved in decisions concerning her contact with the boys," Diana's longtime equerry Patrick Jephson writes in Shadows of a Princess.

"I do not think she ever got an entirely satisfactory answer, but I doubt if one was possible. It was hard for her to be content with the reality of her reduced influence over her children's activities."

More than that, at the time, Diana was newly-separated and grew deeply jealous. Tiggy's closeness and comfort with all three men was regularly on galling display for the Princess.

Tiggy was clearly just not another member of Charles' retinue.

Paparazzi photos of the Prince greeting her warmly and kissing her on the cheek only fed speculation that Tiggy and the future king were entwined in a clandestine affair.

Affair rumours

According to Diana's former equerry Patrick Jephson and former butler Paul Burrell, throughout 1995, Diana grew obsessed with the idea that Charles and Tiggy were having an affair.

"The Princess developed an increasingly lurid fantasy picture of Tiggy's private life. No man in the Prince's entourage was safe from her, including the Prince himself," Jephson writes in Shadows of a Princess.

However, Diana's suspicions about Tiggy would only get more outrageous.

During an inquest into her death, it emerged a note written by one of Diana's lawyer Lord Mishcon after a meeting with the princess in October 1995 detailed her fears that Charles would have her (and Camilla) both killed to "make way" for Tiggy as his future wife.

"It was ludicrous but at the time, she was beleaguered and felt isolated," a friend of the princess told the Daily Mail. "Also, at the time, Charles was being encouraged to drop Camilla, and it's easy to see how the idea of the personable Tiggy — who was single and well-connected — becoming close to the Prince could take a grip in the princess's mind."

'So sorry to hear about the baby'

By Christmas 1995, Diana was poised to swoop. Totally unfounded rumours had swirled that Tiggy had an abortion after becoming pregnant by Charles.

According to Diana's butler Paul Burrell, the Princess had launched a "top secret" investigation into the gossip and by the time of the Christmas party, saw an opportunity to strike.

"Horror paralysed Tiggy's face. Tears welled in her eyes and she left the room accompanied by Prince Charles's valet Michael Fawcett," Burrell wrote in his book, A Royal Duty.

Paul Burrell says the princess grew obsessed with the idea that Charles and Tiggy were having an affair. (Photo / Supplied)

Tiggy strikes back

In the days after the now infamous Christmas party, Tiggy got in touch with her lawyers who instructed Diana to stop spreading these rumours.

Not only that, but the Queen's private secretary Sir Robert Fellowes (who was married to Diana's sister Lady Jane) launched an investigation into the incident.

According to The Telegraph, he later wrote to Diana: "Your allegations concerning Tiggy Legge-Bourke are completely unfounded. Her relationship with the Prince of Wales has never been anything but a professional one.

"On the date of the supposed abortion, she was at Highgrove with William and Harry. It is in your own best interests that you withdraw these allegations. You have got this whole thing dreadfully wrong."

After Paris

Only two years after Diana's death in 1997 in Paris, it was Tiggy who would provide the essential emotional support for the bereft young princes.

In 1999, Tiggy wed childhood sweetheart Charles Pettifer and left the Prince's employ. (Harry is rumoured to have gotten so drunk at her wedding that he ate a live goldfish out of a centrepiece.)

Despite no longer being on the royal payroll, she remained close to Wills and Harry. She made Harry a godfather to her first son Fred, and Wills is godfather to her other boy, Tom.

In 2011, Tom (then aged eight) was a page boy at William and Kate's wedding while the following year, Harry was beside Tiggy in the audience to watch his godson Fred appear in a school play.

In fact, Tiggy and her family have been quietly involved with every significant moment in Wills and Harry's lives for the last two decades.

Prince Charles and Tiggy Legge-Bourke hit the slopes. (Photo / Getty)

However, Tiggy's life couldn't be more different from the glamorous one she enjoyed flitting about in royal jets.

Today, she lives in Wales with her husband, two stepsons and two sons and runs a $180-a-night B'n'B, where guests are invited to help themselves to biscuits and whiskey.

In January 2018, Prince Harry, on an official trip to Cardiff, made a 65km detour during a busy day of activities. He had with him his new fiance Meghan Markle and there was one person he wanted to introduce her to — Tiggy.

Given the now 54-year-old was photographed arriving at Windsor Castle last weekend, it would make perfect sense if Harry would call on the one woman who has proven to be a lifelong dependable source of love and affection, to care for his own son.

It's hard to think of anything that would have made Diana more angry.