graham,

you may know that orson welles did a prequel to the movie in a radio series entitled "the lives of harry lime." welles was a true genius ala "war of the worlds" c1938-39. you may enjoy listening to the entire 52 episodes of the harry lime series here:

http://www.archive.org/details/TheLivesOfHarryLime

hope you enjoy it.

listen guilt-free. it's in the public domain.