It is a pleasure to recognize the help of my editor, Vickie Kearn, for her unstinting patience and understanding; Jon Wainwright, who typeset the book so expertly and sensitively; Sean Kureshi, Andrew Leigh and George Watkinson for their expertise in computer graphics, ancient Greek and phi from a sound engineer’s point of view respectively. And finally a very special mention to Ardavan Afshar and Archie Bott, two former students who read the manuscript so carefully and freely commented on it; by so doing they were of inestimable help.