The Duke of York overcame his "sense of trepidation" to abseil down the tallest building in Europe for charity on Monday.
Andrew descended the Shard skyscraper in London, beginning his daredevil stunt from the 87th floor - just below the top of the 1,016ft tower - and finishing half an hour later on level 20.
The 52-year-old royal was one of around 40 people to lower themselves to raise money for educational charity the Outward Bound Trust and the Royal Marines Charitable Trust Fund.
The Duke on his way down the London landmark
Making it safely down after abseiling a total of 785 feet, Andrew said: "I'm not even going to say that was a piece of cake or not. I will never do it again.
"I have to say, the most difficult bit was walking up the stairs."
Donors have given more than £290,000 to sponsor Andrew, who is the Outward Bound Trust's chairman of trustees.
As a former Royal Navy helicopter pilot who served in the Falklands War, he said the Marines were especially close to his heart.
The Shard is Europe's tallest building
Describing how he got ready for the challenge, he said: "You have a moment to realise what you are doing and where you are going to go.
"The difficult bit was actually stepping out over the edge so the training I had done over the summer with the Royal Marines in Arbroath gave me the confidence to step out over the edge without too much trepidation."
Andrew said he came up with the idea of abseiling down the Shard as a fundraising opportunity last year, when the skyscraper was being built.
The money raised for Outward Bound will be used to fund outdoor activities and learning for children who live in inner cities.
Asked what the Queen thought about his descent, the Duke of York said: "When I spoke to her last at Balmoral she was interested in why we were doing it and when I spoke to her about all the safety and the activities that were going on around it, about the teamwork... she understood what all the risks were and, like the incredible monarch she is, she was entirely happy.
"But this is not about me, this is about young people, this is about young people's future, this is about changing people's lives and giving them the opportunity."
After Andrew completed the first descent of the day, he was followed by Foreign Secretary William Hague's wife Ffion, who is Outward Bound's deputy chairman.
Mrs Hague described abseiling from such a height as "scary, exhilarating and truly terrifying" and said her husband thought she was mad when she first mentioned the idea.
She said: "I am very glad it is over and I wouldn't necessarily want to do it again but, my goodness, I am glad I have done it.
"I was trying very hard to focus on remembering the view because very few people in London will have seen London from that angle, from this fantastic building.
"There have been millions of moments when I have thought 'I am not going to be able to do it' but the training has been fantastic and we just kept focusing on the possibility of raising £1 million for Outward Bound. That's got to be worth it."
Also among the participants was adventurer Sir Chris Bonington, whose long career has seen him conquer mountains such as Everest, the Eiger and Annapurna.
The 78-year-old said: "It was absolutely brilliant. It was just great fun and the view from the top of the Shard is just mind-blowing.
"It is a whole sight easier abseiling down glass than it is rock and snow with the wind whistling around your ears."