We are talking about ITV broadband which shows old programmes!

Okay, but you were asking about the original broadcaster. That's Children's ITV, not ITV Broadband.

Either way, they'd still need to negotiate a new contract with Granada Media/Anglia before broadcasting Knightmare, or they'd be breaking the law. To the best of my knowledge, there's no 'automatic-reversion-of-rights' to the original broadcaster. Which is a shame looked at some ways.

(Rights to the format for making shows can revert from a studio to the creators after about seven years, which is why it was possible for the KMVR remake to be attempted, but re-broadcast of material that's already been produced has to be renegotiated every time.)

Good idea! As challenage haven't renewed their contact, doesn't the rights go to the origanal broadcaster?

No, CITV would have to renew their own contract with Anglia if they wanted to broadcast the series again. It looks very unlikely that they'll ever do that, as it's against their policy to reshow old gameshows.