Dynamo had the Prince of Wales hiding behind his hands as the TV illusionist appeared to break his own fingers.
Prince Charles put his hands over his face as the magician bent his fingers into an unnatural position.
The stunt came just moments after Charles was left stunned by the magician's card trick at a Clarence House reception for his youth charity, the Prince's Trust.
Dynamo, who set up as an illusionist with help from the charity, said: "He (Charles) said 'It must take years and years to perfect that stuff, it really is magic'.
"He was saying 'Your hands are really flexible, even with the shuffling'. I said 'Yes - look how flexible they are', and then I broke my fingers and put them back together again."
Dynamo added: "Charles seemed to like (the fingers trick) but in a fashion that he couldn't look at it."
During the reception, the Prince also revealed that Skyfall is one of his favourite James Bond films, and he is a big fan of its director, Sam Mendes. Naomie Harris, who stars in the film, said: "He (Charles) really enjoyed it. He said it's one of his favourites and he thought that it was one of the best he's seen.
"He thinks it's largely because of having Sam at the helm directing. He thinks it's all about having a great director. I said 'Thank you very much' - it's quite a compliment so I was very pleased to hear that."
The event was held to celebrate the creation of 100 job ambassadors by the Prince's Trust. The ambassadors - who have all faced long-term unemployment before turning things around with the help of the trust - have supported 100,000 other jobless youngsters to develop new skills and access jobs in their community.
US star Will.i.am, who donated his £500,000 salary from last year's BBC One series of The Voice to the Prince's Trust, said: "The way the world is going, you want young kids in inner cities to grow up being part of the conversation not to get jobs but to create jobs."