Britain's Queen Elizabeth was introduced to President Gerald Ford's son when he was "half dressed."
Maria Downs - who served as social secretary to the late former American president and his wife Betty - has revealed Jack "burst in" on the monarch with bare feet and his shirt untucked, much to the embarrassment of his parents.
She said: "There's Jack, shirt tails hanging out and no shoes on being introduced to the queen by Mrs. Ford."
"He said, 'Whoops!' and ran. Mrs. Ford said, 'I am so embarrassed.'"
But according to Downs, Queen Elizabeth dismissed the incident and even managed to see the funny side.
She added to Britain's The Daily Express newspaper: "The queen laughed and replied, 'Oh don't worry about it. I have one like it at home.' For the longest time, we referred to Jack as 'it.'"
It is uncertain whether the queen was referring to her son Charles - who recently turned 60 - or Andrew, who would have been 16 years old at the time.