Celebrity Traitors contestant Clare Balding made a grave error during the first mission of the BBC series on Wednesday's episode (8 October).
The stars were tasked with dragging a Trojan horse through a series of gates they had to unlock by answering a question correctly, to add £15,000 to the prize pot.
As the contestants were discussing an answer, the broadcaster, 54, accidentally locked in a number before the others came up with a suggestion and appeared to be horrified at what she'd done.