Ian Stewart is emeritus professor of mathematics at the University of Warwick and a Fellow of the Royal Society. Author of more than 140 books and 230 research papers, he wrote Scientific American's "Mathematical Recreations" column for twelve years. David Wood is reader at the University of Warwick's Mathematics Institute, where he was director of undergraduate studies for more than twenty years. During that time he was both a practitioner and consultant with Warwick's National Academy for Gifted and Talented Youth (NAGTY) and the International Gateway for Gifted Youth (IGGY).