Branding vs. Communications Planning

Sometimes people don't quite get the difference between a brand strategy as fixed in a brand book and a workable idea for communications.

"We had that whole brand thing already with another agency. Some brand guys - Soandso and Soandso. So we know perfectly well what our brand is. We have to use what the brand bible says. So why are you telling us we need a real idea, now. Are you crazy? We have it already."

So this is how I once tried to explain why there are two views on "doing the brand thing" and why the brand book doesn't always give you the strategic campaign idea - not even for an image campaign. Not always? I mean almost never.