16 May 1964: broadcast of "The Keys of Marinus", sixth episode of the story we now call The Keys of Marinus. Susan, Barbara and the Doctor expose Eyesen and Kala and liberate Ian; the Voords have taken over the Conscience, but Ian gives them a false key and it explodes.
16 May 1970: broadcast of second episode of Inferno. More slime bubbles up, infecting Stahlman; and the Doctor vanishes, with Bessie and the Tardis console.
16 May 2003: webcast of second episode of Shada. The Doctor, Romana, K9 and Chris find Skagra's invisible spaceship.