When Bob Graham, his wife and three children were invited to afternoon tea with Princess Diana they thought they were in for a nice chat over tea and treats at her luxury hotel overlooking Sydney Harbour.
But when the family arrived they were stunned to find Diana hiding in the dark.
"She had all the blinds closed and we said, 'Why have you got the curtains closed because it's a lovely sunny day'," recalls Prof Graham, who as head of the Victor Chang Cardiac Research Institute hosted the princess during her three-day stay in November 1996.
"She said, 'Well, every time I go out on the porch two helicopters take off wanting to take photos'. So she was virtually locked in this room."
The moment offered a compelling glimpse into Diana's life and her constant battle to escape the prying eyes of the media.
Diana's visit was her final one to Sydney, coming just nine months before her death in a Paris car crash on August 31, 1997.
It was also her first solo visit to Australia following her divorce from Prince Charles.
Diana was in town to raise money for the Victor Chang Cardiac Research Institute, where her secret boyfriend at the time, heart surgeon Hasnat Khan, had trained.
Prof Graham, like the rest of the world, was unaware of the relationship when Diana visited but remembers that while the princess never mentioned Khan she knew an incredible amount about heart disease.
"I was impressed that she wasn't just some frivolous airhead," he said.
"She was someone who was genuinely interested and who had learned quite a lot about medicine and heart disease and had a genuine interest in helping people, and not just because she had someone who happened to be a cardiologist as her boyfriend."
Diana dazzled Sydney's social set at a glittering charity dinner for the institute, where pop star Sting serenaded her and hundreds of people lined the streets to catch a glimpse as she arrived.
"It speaks volumes for the people of Australia that despite the passage of time you've still both recognised and remembered me," Diana told the dinner guests.
The confident princess who took Sydney by storm was a far cry from the shy aristocratic 19-year-old who secretly fled to regional NSW 15 years earlier, just two days after Prince Charles asked her to marry him.
Unbeknown to the world at the time, Lady Diana Spencer spent three weeks with her mother Frances Shand Kydd working on wedding plans while staying with a friend at Mollymook on the NSW south coast and the family's Bloomfield sheep station near Yass in February 1981.
"That was a complete disaster because I pined for him but he never rang me up," Diana later told journalist and author Andrew Morton in a series of taped conversations he used for his blockbuster book, Diana Her True Story.
After their fairytale wedding in 1981 Diana and Charles chose Australia for their first official tour in 1983 - a trip that also caused angst for the princess.
The royal couple brought their nine-month-old son Prince William with them on the six-week tour, which Diana described as "make or break time for me".
She found the crowds overwhelming, confiding in tears to her lady-in-waiting at the end of the first week how she wanted to flee home to London.
Prince Charles was also surprised by how wellwishers were more interested in his new bride than their future king.
"Everybody always said when we were in the car, 'Oh, we're in the wrong side, we want to see her, we don't want to see him,' and that's all we could hear when we went down the crowds and obviously he wasn't used to that and nor was I," Diana told Moreton.
Despite the behind-the-scenes tensions, the tour was judged a success.
The crowds came out in force again when Charles and Diana returned for Victoria's 150th anniversary in 1985, and Australia's bicentenary in 1988 when speculation was mounting about the state of the royal marriage.
In between those official tours Charles rekindled his affair with long-time love Camilla Parker Bowles while Diana embarked on a five-year affair with former British Army captain James Hewitt.
But amid the searing summer heat of January 1988, Diana and Charles put on a good public show of togetherness as they spent Australia Day on Sydney Harbour before touring Darwin, Adelaide and Melbourne.
During a rare public speech, Diana pondered the future.
"Like most people with small children I often wonder what sort of world our sons will inhabit in the next century. When I meet people like you all here today, I am encouraged to believe that the future will, after all, be something to look forward to," she told a crowd in Adelaide.
However Diana's next few years were far from enjoyable, with prince and princess separating in 1992.
Diana was determined to forge her own path and reduce her public engagements, saying she had found the media attention of the past decade overwhelming and wanted to focus on her sons William and Harry.
Her affair with Hewitt had ended a year earlier, but Diana eventually found love again with Pakistani-born heart surgeon Hasnat Khan and even dreamed of moving to Australia with him to escape the Fleet Street press.
The romance fizzled out just weeks before Diana's death after Khan refused to marry her because he had no desire to be thrown into the public spotlight.
Prof Graham says while Diana hated the spotlight just as much as Khan, he was struck by how she tried not to let the media attention stop her from doing what she wanted.
"Her attitude was, not that she ever said it, was she just couldn't give a damn, she just wanted to do what she felt was right, which I thought was very impressive."