It is revealed at the end of the audio that Gerrard is a not a human and that Ian never returned to Earth. Gerrard is an avatar of Hisk's shared collective consciousness, by Limbus. I am not sure what the appropriate name for such a page would be. Perhaps, it could just be called Limbus. But Gerrard is clearly wrong.
Talk about it here.
Gerrard was an avatar used by the shared collective consciousness of the city of Hisk to try to pry out the First Doctor's and Vicki's weaknesses while they were rewriting this consciousness. It pretended to be human detective Gerrard from 20th century Britain interviewing Ian Chesterton about the disappearance of him, Barbara Wright and Susan Foreman. (AUDIO: The Sleeping City)