The Diana Award was established in 1999 in memory of Diana, Princess of Wales, and her belief that young people have the power to change the world.
WATCH: HELLO! Insider - Celebrating Princess Diana
The charity, which runs anti-bullying and mentoring programmes, also rewards young people who carry out inspiring work. Each year, thousands of young people are nominated by individuals and their communities to highlight these selfless acts.
Honouring this year's winners, Prince William wrote: "Congratulations on receiving The Diana Award today! You are part of an inspirational generation of young people who are changing the world through your actions, and I hugely admire your efforts. Your stories are remarkable.
"Many of you face huge challenges in the face of difficult times, yet you are tirelessly breaking down barriers to create a better future for us all. Thank you for your compassion, bravery and absolute determination. You truly are the personification of my mother's legacy and I know she would be so proud of you all."
Prince William and Prince Harry were exceptionally close to their mother
Reflecting on his late mother's work, the royal added: "I believe there's no better way to celebrate her life and work than through recognising incredible people who dedicate so much time and effort to helping those around them. I hope that you stand proud in the knowledge that you are making a real difference and that you enjoy today's ceremony - you deserve it!"
Both Prince William and his brother Prince Harry were exceptionally close to their mother, who sadly died in a car accident in August 1997. The siblings keep the Princess' memory alive and often talk about 'Granny Diana' to their own children.
In ITV's documentary Diana, Our Mother, Harry gave an insight into his mother's cheeky side, saying: "She was one of the naughtiest parents. She would come and watch us play football and, you know, smuggle sweets into our socks.
"And I mean like literally walking back from a football match and having sort of five packets of Starburst. And just the whole shirt was just bulging with sweets and then sort of looking around, open the tuck box, throw it all in, lock it up."
"She was very informal and really enjoyed the laughter and the fun," William added.
For more information about the Diana Award, visit diana.award.org.uk.
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