I don't think that Blake had Durandal inside him, but Blake COULD have been a false personality created by Durandal.
There's at least one fictional precedent I can think of for a computer faking the presence of a human:
Robert A. Heinlein's "The Moon Is A Harsh Mistress"
Short summary: Technician Manuel discovers that Luna's MYCROFT computer has awakened to sentience. They become friends, and then end up becoming involved in a revolution, finally helping Luna to win its independence from Earth and set up a libertarian/anarcho-capitalist society.
Marathon-ish bits: Mycroft, or Mike, is an A.I. with quite a sense of humor who runs, basically, everything automated in Luna. Mike is able to simulate voices and images - during the height of the revolution, he personally "appears" on television as revolutionary leader "Adam Selene". Mike introduces Earth to the magic of orbital bombardment - with asteroids fired from Lunar catapults.
