Prince Andrew, who has completed his charity abseil down London's Shard building, has told reporters: "The charity [The Outward Bound Trust and the Royal Marines Charitable Trust Fund] is close to my heart given my time in the Navy. It's about getting young people to face challenges."
He said the most difficult part of the stunt was "walking up" to the top of the building because he had time to "realise" what he was doing.
Yes I did enjoy it. I was curious to see if I would be able to step over the edge! I was scared yes.
There is a moment of trepidation when you step out.
More top news
Headliners taking to the stage during the weekend will be Kasabian, Depeche Mode, Liam Gallagher and The Killers.
Official statistics show there were 82,694 inmates in jails in England and Wales on Friday.
Fears have been raised about the safety of the structure after the blaze last Friday night.