Of the published forms of "The Hitchhiker's Guide to the Galaxy", which came first chronologically?

"The Hitchhiker's Guide to the Galaxy" was first a BBC radio series, airing in 12 parts in 1978. It was written by Douglas Adams. The series is best described as comic science fiction and follows the main character, Arthur Dent, through his adventures in space with his friend, Ford Prefect. Both (in the picture) were "advised" through their adventures by an electronic reference/guide book, "The Hitchhiker's Guide to the Galaxy". Some have suggested that Adams predicted the popularity that would be gained by the Internet through this guide.

The radio series proved popular and Adams wrote a five-book extended companion to the series which he described as a "trilogy". The original 12-part series was turned into two books, "The Hitchhiker's Guide to the Galaxy" and "The Restaurant at the End of the Universe" (both published in 1979); "Life, The Universe and Everything" (1982); "So Long and Thanks for All the Fish" (1984) and "Mostly Harmless" (1992). These books then spawned other radio series.

A TV series made by the BBC first aired in January 1981 and used the original Adams radio scripts.

Adams died on May 11th 2001.

A film, directed by Garth Jennings, was released in 2005, starring Martin Freeman (Arthur) and Yasiin Bey (Ford). The series has also been made into a stage play (1979) and a video game (1982-84).

Chronology therefore: - Radio: 1978; Book: 1979; TV: 1981; Film; 2005.