Sir Humphrey: With Trident we could obliterate the whole of Eastern Europe.
Jim Hacker: I don't want to obliterate the whole of Eastern Europe.
Sir Humphrey: It's a deterrent.
Jim Hacker: It's a bluff. I probably wouldn't use it.
Sir Humphrey: Yes, but they don't know that you probably wouldn't.
Jim Hacker: They probably do.
Sir Humphrey: Yes, they probably know that you probably wouldn't. But they can't certainly know.
Jim Hacker: They probably certainly know that I probably wouldn't.
Sir Humphrey: Yes, but even though they probably certainly know that you probably wouldn't, they don't certainly know that, although you probably wouldn't, there is no probability that you certainly would.

– They know if they launched an attack. I'd press the button.
– You would?
– At the last resort, yes, I certainly would.
– And what is the last resort? … If they try anything, it will be salami tactics.
– Salami tactics?
– Slice by slice. One small piece at a time. So will you press the button if they invade West Berlin? Riots in West Berlin, buildings in flames. East German fire brigade crosses the border to help. Would you press the button…? The East German police come with them. Then some troops, more troops just for riot control, they say. And then the East German troops are replaced by Russian troops. Button…? Then the Russian troops don't go. They are invited to stay to support civilian administration. The civilian administration closes roads and Tempelhof Airport. The Russian army accidentally on purpose cross the West German frontier. Suppose the Russians have invaded West Germany, Belgium, Holland, France? Suppose their tanks and troops have reached the English Channel and are poised to invade? Is that the last resort?
– We'd only fight a nuclear war to defend ourselves. That would be committing suicide!
– So what is the last resort? Piccadilly? Watford Gap service station? The Reform Club? Maybe the nuclear deterrent makes no sense.
– Yes, it does. If the Russians or Americans have the bomb, so must the other side.