Sarnidac the Dwarf wrote:
 Sir Humphrey emphasizing that he had studied at Oxford, and not at Cambridge, and so could not have been spying for the Russians.

That being a reference to Kim Philby, Guy Burgess, and the others of the Cambridge Five.

I once hear an Australian retired politician say, "Yes Minister is seen all over the world as a comedy.  Thos of us who have actually been in government recognize it as a documentary."

He was absolutely right.