Prince William says Queen Elizabeth helped him come to terms with the death of his mother.
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The 33-year-old royal tragically lost his mother, Princess Diana of Wales, in 1997 when he was just 15-years-old and says the Queen has been there for him and "understood some of the more complex issues when you lose a loved one".
He said: "She's been a very strong female influence. 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 and who's been there and who has understood some of the more complex issues when you lose a loved one ... So she's been incredibly supportive and I've really appreciated her guidance."
During the documentary for Sky News, the Duke of Cambridge also recalled a time in his childhood when he was given a real telling-off by the 89-year-old royal.
Speaking in The Queen At 90, he added: "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.
"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."