Queen Elizabeth wasn’t a fan of one of her late husband Prince Philip’s practical jokes. Prince William revealed in the BBC One film Prince Philip: The Royal Family Remembers that a messy prank of his grandfather’s used to get the Duke of Edinburgh in trouble with Her Majesty.

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“He used to take the lid off [the tube] and put it in your hands... and then he‘d squish your hands together to fire the mustard onto the ceiling,” William recalled (via BBC). “He used to get in a lot of trouble from my grandmother.”

The Duke of Cambridge noted that his grandfather, who was “the heart of the family,” enjoyed those jokes. William said, “He enjoyed messing around the children and being a grandfather.”

William’s cousin Zara Tindall also shared memories of her grandfather getting mustard on the ceiling. “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,” she said in the upcoming documentary. Zara’s brother Peter Phillips added, “I actually think the marks are still there.”

Prince Philip: The Royal Family Remembers, which was “originally conceived to mark” the Duke’s 100th birthday, features the Queen and Philip’s four children (Prince Charles, Princess Anne, Prince Andrew and Prince Edward), “along with their adult grandchildren and other members of the Royal Family.”

The special was filmed before and after Prince Philip passed away in April. The documentary-makers met with the late royal’s “long-serving staff and to capture his study, private office and library, exactly as they were during his seven decades at the heart of royal life.”