Ex-royal butler reveals monkey business at palace
He recalled how he regularly used to pass the ballroom at Sandringham House and see Prince Charles and William and Harry bouncing on a trampoline.
"Prince Charles used to set up a trampoline in the ballroom and when you went past, you could see him and the boys jumping up and down on it," he said.
And he revealed that one member of staff regularly dressed up in a gorilla suit and ran around Buckingham Palace, surprising his colleagues - and even some members of the Royal family.
"He usually just stuck to the staff quarters, jumping out at us from behind doors roaring and so on," said Mr Campbell.
"But sometimes he would run past Princess Anne's apartments - but never near the Queen's room, he knew not to do that. When Princess Anne saw him, she would have a good laugh and roar back at him."
He added: "I remember one year, at Christmas, one of the butlers played a joke on the family and took a toy parrot that recorded everything you said and repeated it back.
He put it on a silver server with a big lid and presented it to the Duke of Edinburgh at dinner.
"He said: 'What is that? What is going on?' and the parrot just shouted it back at him. The Duke found it very funny."
And Mr Campbell, who admits the Queen often caught him and other butlers hiding in the vaults eating the leftover desserts after a lavish meal, said the family were just like any other.
"They liked to have fun and they had such a great sense of humour," he said.
"They were a fantastic family to work for."