The "Tiny Dancer" singer recalled an incident he witnessed between the British monarch and her nephew, Viscount Linley.
According to a report in the Sunday Times of London, John writes of attending a party where Queen Elizabeth asked Linley to watch his sister, Lady Sarah Armstrong-Jones, because she had left the party due to feeling ill. But Linley wanted to stay and enjoy the festivities and his aunt did not like that.
"When he [Linley] repeatedly tried to fob her off, the Queen lightly slapped him across the face, saying ‘Don’t’ – slap – ‘argue’ – slap – ‘with’ – slap – ‘me’ – slap – ‘I’ – slap – ‘am’ – slap – ‘THE QUEEN!'" John writes in his book according to the outlet.
Linley then took his aunt's instructions to heart.
"I know the Queen’s public image isn’t exactly one of wild frivolity, but...in private she could be hilarious," John wrote.
The 72-year-old also dished on other stories about the British royal family in the upcoming book.