During a programme honouring the Queen for her 90th birthday, the Duke of Cambridge says the telling off from his grandmother has stuck with him throughout his life.
The royal telling off came to William while he was a child playing at his grandmother's Scottish estate, Balmoral. He and his cousin Peter Phillips were riding a quad bike around the grounds.
He said: 'We were chasing Zara around who was on a go-cart, and Peter and I managed to herd Zara into a lamppost and the lamppost came down and nearly squashed her and I remember my grandmother being the first person out at Balmoral running across the lawn in her kilt.
'She came charging over and gave us the most almighty b******ing, and that sort of stuck in my mind from that moment on.'
But this isn't the first time William has spilled the beans about right royal telling off. Earlier this year Prince William shocked audiences with his swearing when he told a story about receiving letters at boarding school from his father Prince Charles that sometimes contained a 'b******ing', as he put it.
In a more emotional part of the recent documentary William also told how the Queen had helped him after the loss of his mother, Diana. The Duke said, 'She's been a very strong female influence and having lost my mother at a young age, it's been particularly important to me that I've had somebody like the Queen to look up to.
'[She's someone] who's been there and who has understood some of the more, um, complex issues when you lose a loved one.
'So she's been incredibly supportive and I've really appreciated her guidance.'
The programme will be shown tonight, on Wednesday the 20th of April, at 9pm on Sky News.