The 46-year-old singer stained the British monarch's carpet when he attended the Duke of Edinburgh's Awards in May 2019 at the royal residence in London.
Peter was "honoured" to have been invited to the event with his wife Emily but things took an embarrassing turn when his hot beverage tumbled out his hand onto the lush flooring.
Writing in his New! magazine column, he said: "I was in this beautiful room, which had the best carpet I've ever seen and, me being me, I tipped a cup of black coffee all over it. I was freaking out and begged the royal staff not to tell the Queen. She might have made me pay for it, which would probably have cost more than the whole village I live in!"
The 'Mysterious Girl' hitmaker spilled the beans following Olivia Coleman disclosed her husband stole toilet roll from their visit to the palace.
The 'Crown' actress' spouse Ed Sinclair - with whom she has three children - were meeting Prince William at a charity event at the royal residence when he swiped the paper.
Olivia admitted: "Since getting the part, I've met the Queen in a line-up at the BFI, and the lovely Prince William at a charity do at the palace. I was very uncool, and he was charming. He has that thing where he makes you feel you're the most exciting person in the room ... Then my husband stole some loo roll just to say we got it from Buckingham Palace. If we can get away with that, we can get away with this programme."
Sharing his opinion of the toilet roll theft, Peter said: "The Oscar-winning actress ... now joins the likes of Emma Bunton and Piers Morgan, who've both nicked trinkets from the Palace. Tut-tut!"