"Thank you for being the friend that you were to my mum. Thank you for being our friend, thank you for being a friend to our kids", Harry said in the video. "Even though this is officially your retirement, this will not be your last gig, we know that, but we love you, and congratulations on an incredible career."
The couple also congratulated the 75-year-old singer on his achievements in the entertainment industry.
John is a long-time friend of Harry's and has known the duke since he was a child, through his close friendship with Harry's mother, Diana. He famously performed at the late Princess of Wales' funeral, tweaking the lyrics of his song Candle in the Wind to reflect Diana's life.
How did Diana meet Elton John?
John has been friendly with various members of the Royal Family for decades. In previous years, he notably attended events with Princess Margaret and concerts for the Princes' Trust, as well as being a guest at several royal weddings.
Diana first met Elton John at Prince Andrew's 21st birthday party. The singer was performing at the event at Windsor Castle and is reported as saying: "When I arrived there was no one there but the dance band and Princess Diana. We danced the Charleston alone on the floor for twenty minutes."
Read more: When and why did Charles and Diana divorce?
The two became fast friends, with John writing in his 2019 autobiography that "over the years [he] 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".
When did Elton John meet Prince Harry?
The singer first met Prince Harry when he was a young boy, during a lunch that Diana hosted at Kensington Palace for him and Gianni Versace.
John has said that the young Harry was "extremely shy and sweet" and that he appreciated that has remained close with the prince into adulthood: "what a joy it has been to see that young boy grow up and inherit his mother's warmth, sense of humour and courage to stand up and champion the causes he truly believes in."
The singer also said, "Prince Harry has the rare ability to walk into a room full of strangers and make everyone feel comfortable and at ease." This is a trait that John also credited Diana with, saying in his autobiography, "she was blessed with an incredible social ease, an ability to make people feel totally comfortable in her company".
The singer has worked with the duke on various charitable causes over the years and performed at his wedding in Windsor Castle, as well as being invited to Prince William's 2011 nuptials.
In 2019, John posted on Instagram defending Harry and Meghan against criticism about their use of private jets. He wrote: "I am deeply distressed by today's distorted and malicious account in the press surrounding the Duke and Duchess of Sussex's private stay at my home in Nice last week."
The singer added that, "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 unnecessary press intrusion".
John concluded his impassioned post by "calling on the press to cease these relentless and untrue assassinations on [Meghan and Harry's] character that are spuriously crafted on an almost daily basis."
The 'deep freeze' - Elton John and Diana fall out
It wasn't always smooth sailing for the singer and the princess — not long before her death, the two had a falling out and didn't speak for some time.
Tina Brown — former editor of Vanity Fair and royal author — termed this period of Diana's life the "deep freeze" during which she also lost touch with many former confidantes, including Sarah Ferguson, the Duchess of York.
In his autobiography, John wrote that at the time he was worried about Diana during this period: "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 here", adding that it "wasn't a healthy situation."
Brown has written that the pair fell out over a "coffee table book" the royalties of which were to be donated to "John's aids foundation." Brown claimed that the issues was that "pictures of members of the Royal Family, including one of the princess and the boys, appeared amid a portfolio of semi-nude male models and Diana feared that would upset the Queen."
John clarified later despite claiming otherwise, Diana had known what was to be in the book and "said she loved it", as well as agreeing to write a forward for it. When she dropped out of doing so last minute, John "wrote back to her, calling her out, telling her how much money she had cost the AIDS foundation".
Diana's response was, according to John, "formal and severe", and the two friends only reconciled later after tragedy struck.
On July 15 1997, the pair's friend, fashion designer Gianni Versace, was murdered outside his Miami home.
They got back in touch and attended the designer's funeral together, however, the reconciliation was to be short lived: Diana died in a car crash only a few weeks later.
Candle in the Wind
Famously, John performed at the funeral of his friend in 1997, singing a version of Candle in the Wind with lyrics adapted for the occasion.
The performance very nearly didn't happen, with papers released from the National Archives in 2021 showing that the Dean of Westminster had to write a persuasive letter to the palace to get them to sign off on the tribute performance.
The Very Reverend Dr. Wesley Carr argued that even "if it were thought that the words were too sentimental", by the palace, "it would be imaginative and generous" to the public to let John perform, he also wrote that they "would urge boldness" as the performance would be "something of the modern world that the princess represented".
John donated £37m from the royalties of the song to Diana's charitable foundation and said of the performance in 2008, "what was going through my mind was: 'don't sing a wrong note. Be stoic. Don't break down and just do it to the best you can possibly do it without showing any emotion whatsoever.' My heart was beating quite a lot I have to say."
The singer has also said that except at the funeral, he "would never, ever" perform either version of Candle in the Wind in front of William and Harry, and that despite the songs success in the charts, he "would have preferred not to have made the record and [Diana] to still be alive, but it was what it was."
John wrote in his autobiography that he thought the expectations placed on his friend's sons were "inhumane". William and Harry, "were forced to walk through the streets of London behind their mother's coffin, told to show no emotion and look straight ahead" which, John added he believed "was a horrendous way to treat two kids who'd just lost their mum."
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