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.
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Five people were killed and dozens more were injured after a car and knife attack in the capital on Wednesday afternoon.
Among those expected to attend the ceremony will be former US President Bill Clinton and ex-Northern Ireland first minister Peter Robinson.
Five people have been killed and 40 injured after a car and knife attack in London on Wednesday.