broadcast anniversaries 14 March 1964: broadcast of "The Wall of Lies", fourth episode of the story we now call Marco Polo . Marco Polo confiscates the Doctor's spare Tardis key; Tegana continues to plot against him. 14 March 1970: broadcast of seventh episode of Doctor Who and the Silurians . The plague is cured, the Silurians return to hibernation, and the Brigadier blows up their caves. 14 March 1981: broadcast of third episode of Logopolis . Nyssa arrives at Logopolis; the Master has sabotaged the city and it collapses. But will he bring the rest of the Universe down with it?