10 February (production)


 * 1981 - Producer John Nathan-Turner sent a memo to costume designer Colin Lavers, telling him to retain the question mark lapel in the Fifth Doctor's costume. "I do feel that the Doctor Who shirt with the '?' mark on the lapels is worth hanging on to," wrote Nathan-Turner. (REF: The Fifth Doctor Handbook)
 * 2006 - The shooting scripts for The Impossible Planet and The Satan Pit were prepared. (DWMSE 14)
 * 2011 - Recording for Hexagora took place at The Moat Studios.