Oh, this was brilliant. You have the characters' voices down perfectly - I especially love the way you write Romana and Ace. I also adore the parallel between the first and last minute, between the Doctor abandoning Gallifrey and never being able to go back. (At least, that's what I thought it was. I don't want to make assumptions, but the last minute sounds like it takes place during the Time War, what with the temporal instability.)