By the time Elton John was heading into Windsor Castle for Prince Andrew’s 21st birthday party in 1981, he was no stranger to royal affairs. The Queen Mother and Princess Margaret had long been fans of the musician since the 1970s and he had become a staple to the most intimate family events.

On this particular occasion, John had been asked to perform with percussionist Ray Cooper and when he arrived, he found a quiet disco in the ballroom. Before he knew it, John found himself dancing with Princess Anne and Queen Elizabeth II, as she clutched onto her handbag, and they all grooved to Bill Haley’s “Rock Around the Clock.” “I tried my best to come up with a facial expression that suggested this was a perfectly normal state of affairs,” John wrote in his 2019 autobiography Me.

But all that changed with Princess Diana showed up. “She was blessed with an incredible social ease, an ability to make people feel totally comfortable in her company,” he wrote. “That night in 1981, she arrived in the ballroom and we immediately clicked. We ended up pretending to dance the Charleston while hooting at the disco’s feebleness.”

From that moment, a bond was formed, one that would lead them through both heights of their careers, as well as tragedies in their friend circles. “Over the years I knew her, she was fabulous company, the best dinner party guest, incredibly indiscreet, a real gossip: you could ask her anything and she'd tell you,” John wrote.

John witnessed Diana’s effect over men like Richard Gere and Sylvester Stallone

The famous friends were often spotted at major events, like chatting backstage at the 1985 Live Aid concert and John performing for Diana at a 1997 concert for the Prince's Trust.

But it was behind closed doors that they truly began to understand one another. John recalled a dinner party he hosted with Richard Gere and Sylvester Stallone as guests — along with a very single Princess Diana.

“The most peculiar scene developed. Straight away, Richard Gere and Diana seemed very taken with each other,” John wrote. “They ended up sitting in front of the fireplace together, locked in rapt conversation.”

But he soon realized things weren’t quite right: “As the rest of us chatted, I couldn't help notice a strange atmosphere in the room. Judging by the kind of looks he kept shooting them, Diana and Richard Gere's newly blossoming friendship was not going down well with Sylvester Stallone at all.”

John says there was a thwarted fistfight between the two movie stars and ultimately Stallone left in a huff. Throughout it all, Diana held her composure. “She seemed completely unruffled,” he wrote. “Maybe she hadn't realized what was happening. Or maybe stuff like that happened all the time and she was used to it.”

That was when John came to realize the power the princess held. “If I was bowled over by Diana, it was nothing compared with the impact she could have on straight men. They seemed completely to lose their minds in her presence: they were just utterly bewitched.”

Princess Diana chatting with Elton John and George Michael at the Feed the World Live Aid concert in July 1985

Princess Diana chatting with Elton John and George Michael at the Live Aid concert in July 1985

John hit a 'deep freeze' with the princess

Whatever that intangible effect was that she had on men, John also realized that her true power came through in her selfless show of humanity. “That famous photo of her holding an AIDS patient's hand at the London Middlesex Hospital — that was Diana,” he wrote in his book. “I don't think she was necessarily trying to make a big point, although obviously she did: in that moment, she changed public attitudes to AIDS forever.”

Even so, their deep friendship hit a trouble spot — which Tina Brown called a “deep freeze” in Vanity Fair — over a 1997 coffee table book, Rock and Royalty, created with Gianni Versace to benefit the Elton John AIDS Foundation. The book had photos of the royal family, including one of Diana and her sons Prince William and Prince Harry, among photos of semi-nude male models. She had also agreed to write the book’s forward. But suddenly, she pulled out — very last minute.

“Diana feared that would upset the Queen,” Brown wrote, but that wasn’t the story John was told. “She said she had no idea of the book's contents, which just wasn't true: Gianni had shown her the whole thing and she had said she loved it,” he wrote.

Confused, he reached out to try to straighten things out. “I wrote back to her, calling her out, telling her how much money she had cost the AIDS Foundation, reminding her that she had seen the book.”

In response, he received a “formal and severe” letter than began, “Dear Mr. John.”

The cold response infuriated John, who considered the princess a dear friend. But his emotions ran deeper. He was concerned about her. “She seemed to be losing touch with all sorts of really close friends, who would be honest with her, and surrounding herself instead with people who told her what she wanted to hear,” he wrote. “I knew from personal experience that wasn't a healthy situation.”

But the rift was there. “It’s one of those things that friends sometimes do,” John told CNN of their falling out. “You know, they’re too proud to pick up the phone.”

READ MORE: Why Princess Diana Risked Her Life for Humanitarian Causes in Africa

The sudden death of Versace reunited the friends

Sadly, it took a tragedy — the brutal murder of mutual friend Versace in July 1997 — for the two to find their way back to one another. As soon as the news spread, John found Diana on the other end of the line. “I don't even know how she got hold of the number; we hadn't had the house in Nice for long,” John wrote in his autobiography. “She was just down the coast, in Saint-Tropez, on Dodi Fayed's yacht. She asked how I was, if I'd spoken to Donatella. Then she said: ‘I'm so sorry. It was a silly falling out. Let's be friends.’”

Friends again, Diana sat next to John at Versace's funeral. During the services, a photographer took a now-famous photo of what appeared to be Diana leaning towards John to console him. But John eventually revealed the truth about the moment: “They snapped her just as she was leaning past me, reaching for a mint that David [Furnish] offered her. The warm words of comfort coming from her lips at that exact moment were actually: ‘God, I'd love a Polo.’”

Even in their time of grief, they had found some levity — the cornerstone of their friendship.

That reconciliation sparked more letter writing. John wrote her a thank you note, and she responded offering to be a patron of his foundation and asked him to be one for a landmine charity she was working with.

“We were going to meet up next time we were both in London to have lunch and discuss it,” he wrote. “But there wasn’t a next time.”

Elton John singing "Candle in the Wind" at Princess Diana's funeral at Westminster Abbey on September 6, 1997

Elton John singing "Candle in the Wind" at Princess Diana's funeral at Westminster Abbey on September 6, 1997

John called performing at Diana's funeral 'the biggest gig of my life'

On August 31, 1997, John was awoken by the sound of the fax machine with a handwritten message from a London friend saying, “So sorry to hear about this awful news.” Perplexed, he turned on the news and learned that his beloved friend Princess Diana had died in a tragic car crash.

He never expected, just six weeks later, to be sitting at another funeral. This time, he sang “Candle in the Wind” to his friend, with lyrics changed by his writing partner Bernie Taupin to honor Diana with the words, “You called out to our country, and you whispered to those in pain.”

Mourning his friend, the performance was one of the most difficult of his life. “There was a sense in which it was the biggest gig of my life — for four minutes, I was literally going to be the centre of the world’s attention — but equally, it wasn’t an Elton John moment, it wasn’t about me at all,” he wrote.

Ultimately that day, he saw Princess Diana’s legacy in the faces of her young sons. “William and Harry looked completely shell-shocked,” he remembered. “They were 15 and 12, and I thought the way they were treated that day was absolutely inhuman. They were forced to walk through the streets of London behind their mother’s coffin, told to show no emotion and look straight ahead. It was a horrendous way to treat two kids who’d just lost their mum.”

And to this day, John feels that pull to Diana through William and Harry, as he tweeted in August 2019 after an invasion of Harry’s privacy. “Prince Harry’s Mother, Diana Princess Of Wales was one of my dearest friends. I feel a profound sense of obligation to protect Harry and his family from the unnecessary press intrusion that contributed to Diana’s untimely death.”