ShowTime, not starting, just not left at the starting gate.
Certainly in the V-Force, when all around was toast, we would have aborted if we did not get the go message. I have no idea if the CinC had a letter of last resort. According to Hennessey he certainly had the authority.
TTN, it was the Light Service on 200kc/s. Radio 4 Long Wave is now on 198kHz