October 14, 2014 - 17:54 BST hellomagazine.com Princes William and Harry have paid tribute to their late mother, Princess Diana, in the foreword to a new book dedicated to The Diana Award. Princes William and Harry have paid tribute to their late mother, Princess Diana, in the foreword to a new book dedicated to The Diana Award. The charity was set up in 1999, two years after Diana passed away, to tackle bullying and social exclusion and is now celebrating its 15th birthday. "We believe, when encouraged and supported, that young people have the ability to change society for the better", the two Princes write. Prince William and Prince Harry at the 2014 Invictus Games They continued: "We know that our mother - in whose memory this award was established - felt the same and would be proud of its achievements to date." The award also provides training, mentoring and anti-bullying ambassador programmes and the awards are presented to young people, including volunteers, carers and fund-raisers. "Having met young people working with the charity in Newcastle and in London, we were struck in both cases by their deep and lasting sense of social responsibility," added the two Princes. "These young people were working hard to tackle the social issues that affected them - such as bullying or social exclusion - and the Diana Award empowered them to do more." Prince William and Prince Harry with their mother Princess Diana in 1991 The awards ceremony took place on Tuesday at 11 Downing Street, and this year's recipients included 18-year-old Kyle Philips, who received the Diana Champion Volunteer Award. 'It’s a great honour, " he said. "It’s a real privilege to be recognised. I’m really just trying to help the youth in my community." Along with a part time role at a greengrocer, Kyle volunteers more than 500 hours a year at school and leads a group which aims to improve the literacy and numeracy of young boys - many of whom have behavioural or learning difficulties.