I think Mr. Goodwrench, GM Tech, may be a good place to start. But in my experience with RR, they always seem to modify things, for their use. It could as simple as a burned out stop-tail light. Make sure all your tail lights work. Ciao...Paolo
Rolls-Royce Silver Spur? Easy.... slap your chauffeur across the back of the head and tell him what speed you'd like to go. If that doesn't fix it, hire a new driver who'll listen better.
A quick look on google suggests that the cruise control won't work if the 3rd brake light is not working. Also, if it is a mechical system, rather than fully electronic, it's always possible that the vacuum line to the brake override switch has split or come off - do you hear a "hissing" noise down by the pedals?
Thanks everyone, but my third brake light works. I'll have to place an add for a new chauffeur, I think he's the one that spilled the grey poupon. No hissing noises either...