The atmosphere at Wembley Arena is electric as 12,000 10 to 18-year-olds cheer a succession of inspirational speakers at the first ever UK We Day.
Wembley is no stranger to crowds of excitable youngsters. But today is different: the stadium has opened its doors to young people for free - as a reward for charitable acts they have undertaken.
"Both the youths in the audience and the performers on stage have had to earn their way to We Day," Craig Kielburger, founder of We Day, told Parentdish. "People have only been invited to perform if they have a cause that they care about.
"For instance, Prince Harry has done a lot of work in Africa and is very passionate about the environment, while Ellie Goulding has worked with in Kenya, building schools and teaching singing lessons."
We Day has been organised by the charity Free The Children, to encourage young people to volunteer and take action on social issues around the globe. The students were able to earn their place at the star-studded event by undertaking one local and one global charitable act as part of the year-long We Day programme, which Free The Children runs through schools.
The event is being live streamed on AOL UK.
#WeDay Al Gore talking to British children. You can make the world a better place! http://t.co/dS3wv34Y49
- Parentdish_UK (@parentdish_uk) March 7, 2014
Wearing a low key checked shirt, Prince Harry won rapturous applause when he appeared on stage with an apologetic: "For those of you expecting Harry Styles, I apologise and no, I'm not going to sing."
"Everyone one of you has done something amazing to be here," Harry said, adding: "Your actions have, and will, shape our futures.
"We can inspire each other and should ask others to do the same."
Harry was keen to stress that the young activists did not only have to focus on work abroad, but that there was much work to do in their local communities where many children are living with domestic abuse, violence or addiction.
"This is robbing children of their childhood," he said, adding that "the biggest impact you can have is in your community. It doesn't cost a thing, just a little bit of your time.
"Every one of you here has inspired others, please don't stop.
"Some people don't think it's cool to help others. Personally, I think it's the coolest thing in the world."