“Many scholars believe that classical Latin was spoken by almost no one- that it was used exclusively as a literary and scholarly language. Certainly such evidence as we have of everyday writing- graffiti on the walls of Pompeii, for example- suggests that classical Latin was effectively a dead language as far as common discourse was concerned long before Rome fell. And it was that momentous event- the fall of Rome- that helped usher in [English.]”
From The Mother Tongue: English and How It Got That Way by Bill Bryson