This episode was watched by 14.1 million viewers on its original transmission.
This episode includes a line of dialogue in which the Doctor remarks that the Countess is a beautiful woman "probably", which has been used in fandom to suggest the Doctor's character doesn't, or shouldn't, acknowledge the attractiveness of his female companions, a point often brought up when debating the Doctor's romantic entanglements in Doctor Who: The Movie (1996) and the revived series. As it happens, Douglas Adams' previous teleplay, "The Pirate Planet", includes dialogue in which the Doctor directly refers to Romana I as being attractive and having good looks (albeit not in a romantic context), suggesting he was capable of such considerations. Also within this story he does refer to Romana II as being pretty though she is not present at this time.
K9 does not make an actual appearance in this story, but the Doctor does greet him as he enters the TARDIS to go and visit Leonardo da Vinci.