It is the objective of this book to try to give an account of the main lines of these developments. Given the sweep of the subject, I think of the task involved as being in some ways akin to the telling of a long and complicated story: an epic tale stretching over several decades, involving various principal characters that appear and reappear (sometimes in disguised form), and following a complex plot with a number of intricate subplots. To pursue this analogy further, I cannot deny that this book is in part autobiographical: as the narrator of the story, I have chosen to recount those matters I know best by virtue of having first-hand knowledge of their unravelling.