In the film of Hitchhiker's Guide to the GalaxyThe Hitchhiker's Guide to the Galaxy, Arthur saves Ford from being run over, and later Ford saves Arthur from the Earth being demolished.
But in the original radio series and books, we don't seem to be told how the two met, and why Ford would select Arthur (of all Earth's inhabitants) to save.
Putting the film aside, did Douglas Adams ever describe anywhere the circumstances of their meeting, and why Ford chose to save Arthur?