Emma Thompson made a "very loud and inappropriate noise" when Prince William made her a Dame.
The 59-year-old actress visited Buckingham Palace last year to be made a Dame Commander of the Most Excellent Order of the British Empire by the father-of-three.
Speaking on The Ellen DeGeneres Show, Thompson revealed that when she was bestowed with the title, the two "big badges" had to be pinned to her shirt, which accidentally caught her "nipple" prompting her exclamation.
The 60-year-old said: "You get a big old badge - you get two badges."
"Then he had to pin it on and it's a little bit of a nipple moment and you go, 'Gosh, I wasn't expecting that,' then he pins another one underneath. And I'm pretty low slung these days so both times it hurt!"
"I made a very loud and inappropriate noise in Buckingham Palace," she continued.
The Love Actually star has previously revealed the Duke of Cambridge rebuffed her offer of a kiss as he gave her the award.
Thompson recalled: "I said, 'I can't kiss you, can I?' And he said, 'No don't'."
"If you're first up you have to be more formal on such an occasion, but he's looking wonderful and doing so well. He said, 'This day isn't about me, it's about you'."