Prince Harry has called on all people to "embrace regular testing" for HIV and Aids as he paid tribute to his late mother's work in breaking down the stigma attached to the disease.
The royal's comments came as he attended the Attitude magazine awards on Thursday night, where Diana, Princess of Wales was posthumously honoured with the Legacy award 20 years after her death.
Picking up the prize on her behalf, Harry delivered a heartfelt speech about her impact on people affected by HIV and Aids.
Stepping onto the stage to applause from the unsuspecting audience and Adam & The Ants hit Prince Charming, he said: "I often wonder about what she would be doing to continue the fight against HIV and Aids if she were still with us today.
"I believe that she would be telling everyone across society - not just those most at risk - that with effective treatment being free and available in the UK, that we must all embrace regular testing - both for our own sake and for those that we love.
"She would be demanding that same access to treatment and testing for young people in Africa and across the world.
"She would, of course, be standing alongside those who are living openly as healthy, happy and HIV-positive.
"William and I are incredibly proud of what our mother achieved."
Remembering her work before her death in 1997, he said: "She knew that Aids was one of the things that many wanted to ignore and seemed like a hopeless challenge.
"She knew that the misunderstanding of this relatively new disease was creating a dangerous situation when mixed with homophobia.
"So, when, that April, she took the hand of a 32-year-old man with HIV, in front of the cameras, she knew exactly what she was doing.
"She was using her position as Princess of Wales - the most famous woman in the world - to challenge everyone to educate themselves, to find their compassion and to reach out to those who need help instead of pushing them away.
"In the year before my mother's death, the first truly effective anti-retroviral treatments were developed for HIV and Aids.
"She did not live to see this treatment become widely available and save countless lives in the UK and around the world."
As he thanked Attitude for the award, the publication unveiled its new limited-edition magazine cover featuring a black-and-white photograph of Diana by Patrick Demarchelier.