Trivia: For many years, it was thought that every episode of "The Daleks' Master Plan" had been destroyed by the BBC, in their 1970s purge of the archives. However, in 1983, two episodes (5 and 10) were found and returned to the BBC for preservation. They were found in a highly unlikely location: the basement of the Church of Jesus Christ of Latter Day Saints in Clapham, South London. No one knows how they got there.
Trivia: A "missing, believed wiped" episode was found in January 2004, when "Day of Armageddon", the second episode of "The Daleks' Master Plan", was returned to the BBC by an employee of Yorkshire Television. He had rescued the print from destruction in the early 1970s when, as a young BBC engineer, he had found it in a room at the BBC's Ealing Film Studios, which he had been asked to clear of rubbish. He disobeyed the instruction to destroy the episode and took it home with him. Arguably, he stole it from the BBC, but if he hadn't, it would never have survived. In 2013 (I forgot the episode name, but it was the one with Salamander), they found the rest of the films for another episode. The new ones were animated, combined with the already existing ones and released on DVD.