The blonde presenter momentarily lost her cool when Prince Charles and the Duchess of Cornwall visited, posting a picture of herself giving the thumbs up behind the royal couple's backs.
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"Couldn't help it!!! Love it when the royals come to work!! #princecharles #camilla," she captioned the funny image.
The royal visitors sat in on Fearne's Live Lounge segment – which features live performances from popular artists. They watched singer Tom Odell in action.
Charles and Camilla spent the day meeting staff from Radios 1, 2, 3, 4 and the World Service at BBC's London headquarters as part of a day celebrating British radio.