Bob Geldof (left) and Archbishop Desmond Tutu gave inspiring speeches on opening night.Earlier in the day, Haakon had visited schools in the city, but everyone was waiting for him to say something about the recent tragedy in his own country, in which 69 people at a political camp were killed by a lone gunman. Most of them were youngsters.
" One month, 10 days and three hours ago, a bomb exploded in Oslo right outside the government buildings, blowing out windows miles around," he said at the summit's opening night.
"Two hours later, shooting started at an island north of Oslo where youth were gathered, like here, to discuss the issues they see as the most pressing of our time. [A total of] 77 people were killed, and even more injured by the terrorist acts. As Norway is slowly returning to normality, we are struggling to make sense of the atrocities."
"The most important lesson to learn is about ourselves," Haakon (right) told the packed hall at the Kongresshaus. "We cannot undo what has been done, but we can choose what way it will affect us. We can choose to defy brutality with friendship. We can choose to stand by our values. Our challenge is to reach for the light, to reach for the inner best part of us and nurture it.
"The philosopher Kwame Anthony Appiah says: 'It is crucial to remember always that we are not simply black or white or yellow or brown ... Jewish, Christian, Muslim, Buddhist or Confucian, but we are also brothers and sisters; parents and children; liberals, conservatives and leftists; teachers and lawyers and automakers and gardeners ...'
"Now is the time to emphasise what unites us - because we have more in common than what separates us."
The prince's words were followed by music from the Zurich children's choir, Chinese singer Shang Wenjie and a blistering speech from activist-singer Bob Geldof. The Irishman is known for raising money for African countries in crisis. He talked about how the Earth is being sucked dry of resources and how much the poor are suffering. He told the audience: "You have to get us out of this mess, because we have failed."
Undoubtedly the favourite speaker was South African Archbishop Desmond Tutu, who said young people had achieved amazing things in the past and God was counting on them to make a difference now.