Project Zeta Sigma (unproduced TV story)
From Tardis Wiki, the free Doctor Who reference
Project Zeta Sigma was unproduced serial that would have been the first story of the Fifth Doctor. It would not have carried on straight from Logopolis though. It would have featured nuclear disarmament but John Nathan-Turner claimed it would not work and Castrovalva replaced it. (REF: Doctor Who - The Handbook: The Fifth Doctor)
