1. Shada (1979)
BBC
The Episodes: Would-be conqueror of the universe Skagra attempts to locate the Time Lord prison planet Shada and recruit one of its inmates.
The Problem: Technicians' strikes prevented studio scenes from being filmed. Of Doctor Whos many missed opportunities, this is probably the biggest. Douglas Adams worked on Doctor Who as a script editor but only wrote three stories, one of which was Shada. And because Adams was such a gifted writer, it makes this little tale so much more frustrating. Because Shada is the only Doctor Who story in history that had to be abandoned midway through filming. After a number of scenes on location in Cambridge and in studios were completed, the BBC experienced a technicians strike that persisted for the two of the storys filming blocks. The strike was resolved by the start of the story's final filming block but Christmas programming was given priority for studio use, leaving around 50% of the six part story unfilmed and with no hope of it ever being ready before its broadcast date. Despite John Nathan-Turner attempting to remount the story for the following season (Tom Bakers last), these attempts fell through for various reasons and the unfinished scenes were never filmed before Baker left the role. Making Shada Doctor Whos only unfinished story. But even though it was resigned to a fate of being ever incomplete, Shada lived on. A novelisation was published in 2012, an audio adaptation (which was later animated) starring Paul McGann was eventually released, Douglas Adams worked various story elements into his novel Dirk Gentlys Holistic Detective Agency, and finished location footage was used in The Five Doctors to cover Tom Bakers absence. A model of Shada itself was also snuck into the background of the planet factory sequence in the film adaptation of The Hitchhikers Guide To the Galaxy.
Which other Doctor Who stories had behind the scenes problems. Let us know in the comments section below...