Speaking to the 20 honorees and the invited guests, the 34-year-old Duke of Cambridge spoke of his mother's great legacy.
"This summer marks 20 years since my mother died, and she achieved so much in her life," he addressed the audience. "From helping to shatter the stigma around AIDS, to fighting to ban landmines and supporting the homeless -- she touched the lives of millions."
"The truth is, though, that she was taken at only 36, just slightly older than I am today. And of course, we can never know what our mother would have gone on to do," he added. "But in one sense, Harry and I feel that our mother lives on in the countless acts of compassion and bravery that she inspires in others."
Prince William and his brother, Prince Harry, presented the Legacy Award to 20 teenagers from the U.K. and across the world. The Inaugural Legacy Award honored the legacy of their mother through her belief that young people have the power to change the world for the better.
"We are so glad our mother's name is being put to good use through the Diana Award," William said about the event.
Diana died in a car crash in Paris in 1997. In March, William and wife Kate Middleton traveled to Paris for the first time since his mother's tragic death. During their visit, they met with French President François Hollande and attended a series of events, including a reception for young French leaders and a formal dinner at the residence of Her Majesty's Ambassador.