"He used to get in a lot of trouble from my grandmother."
It's long been known that the Royal Family are partial to a practical joke or two.
From the Queen's hilarious prank on a group of unsuspecting tourists at Balmoral, to a young Prince William's easter prank on Princesses Beatrice and Eugenie, it turns out that the royals really do have a royally good sense of humour – despite what The Crown's awkward parlour game scenes might have us believe.
Now, a new BBC documentary has confirmed the late Prince Philip's reputation as resident royal prankster; detailing everything from his fondness for playing tricks on his grandchildren, to his run-ins with "bloody stupid" technology.
Revealing one of his grandfather's signature pranks, which involved an errant jar of mustard, the Duke of Cambridge recalls, "He used to take the lid off [the jar] and put it in your hands... and then he'd squish your hands together to fire the mustard onto the ceiling."
Needless to say, Her Majesty was not amused.
"He used to get in a lot of trouble from my grandmother," William tells Prince Philip: The Royal Family Remembers, which is scheduled to air on BBC One on Wednesday.
Zara Tindall and Peter Phillips also remember their grandfather's mustarding antics, with Zara recalling, "He gets you to hold it in your hands and I can't remember exactly what he says – but he ends up slamming your hands together... it goes all over the ceiling."
Peter adds, "I actually think the marks are still there."
The poignant portrait of the late duke hears from all four of his children, alongside his adult grandchildren and members of his long-serving staff.
William, who remembers his grandfather as "the heart of the family", tells the documentary (as per the BBC), "He enjoyed those jokes, he enjoyed messing around the children and being a grandfather."
Originally conceived as a documentary to mark the duke's 100th birthday, much of the footage was shot prior to Prince Philip's death in April of this year.
"He made time for all of us, he supported all of us - and he kept control of... most of us," jokes Peter Phillips, who recounts his grandfather's run-ins with the latest technology.
"I have memories of him getting a new laptop or a new printer – and hearing him shouting at it. He loved technology... but it was always quite entertaining to see him trying to figure them out!"
Prince Harry also pays tribute to his late grandfather in the doc, saying, "More than anything I miss his humour. But I miss him more for my grandmother because I know how incredibly strong she was with him there."
He adds movingly: "I also know that she's going be OK without him."
Prince Philip: The Royal Family Remembers will air on Wednesday 22 September at 9pm on BBC One.
