The 'Mysterious Girl' hitmaker thought he was going to end up on a prank-style TV show when the former 'Friends' star asked to meet him for a coffee, and he couldn't believe it when the actor met him in person.
He said: "I am such a huge fan of his and the show and honestly thought that when I turned up I'd realise I was on one of those shows like 'Punk'd!' I was thinking, 'Why on earth would such a Big Star want to meet me?' Luckily, David was actually there when I turned up.
"He was planning the renewal of his wedding vows and wanted me to sing at the bash as a surprise for his wife Zoe Buckman. As you'd expect, I was totally chuffed to be asked and jumped at the chance. It's not every day you get to sing at a huge star's party!"
But Peter was unable to sing all The Lines to 'Mysterious Girl' at David's party because he's been suffering from a cut throat, which has become a "real problem" when he performs.
He added to new! magazine: "I've been having major problems with my throat recently and singing is now a real problem.
"I've got a cut on my throat which obviously isn't ideal. I've been seeing a specialist and we are desperately hoping that the muscle will grow over and heal the problem."