The narrator truly had me believing that he is immortal, until the end of the short story. "Mass delusion," I suspected the narrator to be suffering from delusion or just happened to have a childish imagination. His ideas of being a "second-rate New Zealand schoolmaster" must make him confident enough and knowledgeable on history that he could put him self in any time in history and easily talk about it like, as if he was really there. He could start from the first (unofficial) Ice Age, in A.D. 2045 when the Apocalypse happened, or when ever and probably be able to get away with it. He wanted to go extreme and go all the way from the beginning of time where he claims he was alone. Sadly he thinks that will happen again, but in my opinion he'll be alone only in a room with padded white walls. What do you think is he really immortal, or insane?