Lost Episode: 'Chips are Down, Balloon Goes Up, Lights Off'
Many years ago I remember watching an episode of "Yes, Minister" or "Yes, Prime Minister." In one memorable scene they were discussing the effort to close down an empty government building but someone (Sir Humphrey) was arguing that there had to be a place for the government to continue operating in the event of a nuclear war. "You know, when the chips are down, the balloon goes up, and the lights go off! Just because we have annihilation doesn't mean we should have anarchy."
I cannot locate this episode, even though I now own Yes, Prime Minister, the Complete Collection. What was the name of the episode this appeared in? Why isn't it in the Complete Collection?