This was the first episode to show the full-sized TARDIS prop materialising.
This episode takes place in France in July 1794.
This episode was thought lost until 1985, when it turned up in Cyprus, along with the second and third episodes of The Reign of Terror.
According to Susan, the Doctor's favourite period in history is the French Revolution. This was later remembered by Russell T. Davies and Steven Moffat in their writing of the Tenth Doctor, who had a fondness for all things French.
The Earliest Doctor who story to be missing episodes but is mostly complete, Episodes 4 and 5 are currently missing from the BBC Archives and have been restored VIA Animation for an Official DVD release.