Prince Harry shared a late-night joke during his speech, hours after Prince William left the same venue.
The Prince of Wales and the Duke of Sussex both appeared at the Diana Legacy Awards, albeit not at the same time.
Prince William arrived to give a speech in person, while Harry called in via video from his Montecito mansion hours later.
The Prince of Wales was reported to have left the Science Museum at 8.15pm, hours before his younger brother appeared via video.
Prince Harry gave a speech virtually from California
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Harry told the young winners: “I'm sorry I am not there. I wish I could be there with you guys.”
He thanked the group for “for inspiring so many others" and “protecting my mother's legacy”.
The father-of-two later joked with the winners about not getting into “too much trouble” if they planned to head out to the capital to celebrate.
Prince William paid tribute to his mother during his speech, saying she taught him that “everyone has the potential to give something back”.
Prince William giving a speech at the Diana Legacy Awards
PA
William told the audience that he and his wife, Princess Kate, have sought to focus on Diana’s legacy through their work.
He added: “This evening’s Legacy Award is particularly special as it marks the 25th anniversary year of The Diana Award, a charity set up to reflect my mother’s belief that young people can change the world.
“I know that she would have been honoured to see a charity in her name doing such inspirational work to uplift young people from all corners of the globe.”
He said that his mother taught him that “everyone in need deserves a supporting hand in life”.
Prince Harry and Prince William together at the awards in 2017
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William continued: “She taught me that everyone has the potential to give something back; that everyone in need deserves a supporting hand in life.
“That legacy is something that both Catherine and I have sought to focus on through our work, as have the 50,000 young people who have received a Diana Award over the past 25 years.
“I am so proud to see this belief of my mother’s manifested in the amazing young people receiving the Legacy Award tonight.”
After presenting the awards, William met the winners and told them: “The breadth of what you all cover, I’m amazed.
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Princess Diana with her two sons in 1995
PA“I’m so blown away by everything you’re doing because you’re doing it alongside your studies, your lives, your families, everything else.
“There are a lot of barriers I’m sure a lot of you are facing every time you’re doing this.”
William also addressed his walk-on song choice, AC/DC’s song Thunderstruck.
He said: “I like AC/DC, that’s George’s song.”