C19
From Tardis Wiki, the free Doctor Who reference
Department C19 as the British government's liaison with UNIT, an international organisation. (MA: Who Killed Kennedy) During the early 1970s, Sir John Sudbury administrated C19. (MA: The Scales of Injustice)
Behind the Scenes
C19 first gets a mention in Time-Flight. The reference first gets first completley explained in Who Killed Kennedy by David Bailey.