Darcey Bussell is often "disgusted" by Craig Revel Horwood.
The 'Strictly Come Dancing' judge is astonished by her fellow panellist's catty remarks on the BBC One show and admits he never fails to surprise her.
She said: "I'm always shocked. Disgusted. I cannot keep a straight face, but he keeps totally still and never cracks.
"He knows what he's looking for and it's often different from the rest of us."
There has been speculation recently whether Sir Bruce Forsyth, 85, can continue hosting the dancing competition and Darcey admits she doesn't know how long the presenting legend can go on.
Asked if she thinks he can carry on with the show, she said: "I don't know. I'm just lucky that I grew up watching all the incredible shows he's done. He is one of those extraordinary professionals who can pull it off every week."
However, Bruce insists he will go on hosting the show until he can no longer take the physical strain.
He added: "When the time is up I'll be ready for it. I probably won't be very happy about it. But I'll know it's time to go."