NARRATOR: And then one day, nearly two thousand years after one man had been nailed to a tree for saying how great it would be to be nice to people for a change a girl sitting on her own in a small cafe in Rickmansworth suddenly realized what it was that had been going wrong all this time, and she finally knew how the world could be made a good and happy place. This time it was right, it would work, and no one would have to get nailed to anything. Sadly however, before she could get to a phone to tell anyone, the Earth was unexpectedly demolished to make way for a new hyperspace bypass and so the idea was lost forever.

Douglas Adams (1952-2001) English author, humorist, screenwriter
Hitchhiker’s Guide to the Galaxy, Phase 1, “Fit the 2nd” (BBC Radio) (1978-03-15)
    (Source)

Though in the second radio episode, when adapted into the book The Hitchhiker's Guide to the Galaxy (1979), this passage was moved into the Introduction:

And then, one Thursday, nearly two thousand years after one man had been nailed to a tree for saying how great it would be to be nice to people for a change a girl sitting on her own in a small cafe in Rickmansworth suddenly realized what it was that had been going wrong all this time, and she finally knew how the world could be made a good and happy place. This time it was right, it would work, and no one would have to get nailed to anything.
Sadly however, before she could get to a phone to tell anyone, a terrible stupid catastrophe occurred, and the idea was lost forever.