18 December

History of the Doctor Who universe

 * 1926 - Agatha Christie was found at a hotel in Harrogate. (DW: The Unicorn and the Wasp)
 * 1953 - The Sky Gypsy, a small private plane bound from Cardiff to Dublin, disappeared. It reappears in 2007. (TW: Out of Time)

History of Doctor Who

 * 1965 - "Coronas of the Sun" episode 6 of DW: The Daleks' Master Plan was first broadcast.