http://whatculture.com/tv/10-insane-doctor-who-episodes-that-went-unmade.php

Doctor Who vs the Nazis, arcade games and... Derek Acorah?

not to many people are aware of this, but Douglas Adams - former Doctor Who writer and author of the amazing Hitchhiker's Guide to the Galaxy - had a few Doctor Who scripts that weren't used before the original show went off the air and so he turned them into the Dirk Gently's Holistic Detective Agency and Long Dark Tea Time of the Soul books (also AMAZING)