Blue Peacock was the sexy code name of a secret British plan to salt the Rhine with nuclear mines in the 1950s, in case of war.

Less sexily, they planned to put a live chicken in each one, to keep the electronics from getting cold.

When the file was declassified on April 1, 2004, this was taken to be an April Fool’s joke, but it’s true. Fortunately, the project was canceled.