Who is M. de Norpois from Remembrance of Things Past and what is their importance?

M. de Norpois is an ambassador. He is a friend of the narrator's father, in addition to being Mme. de Villeparisis's lover. Norpois encourages the narrator to write, but he dislikes his style of writing. He tells Mme. de Guermantes that the narrator is a "hypocritical little liar".