Robin Wilson is an Oxford graduate, Emeritus Professor of Pure Mathematics at the Open University, and Emeritus Professor of Geometry at Gresham College, London (the oldest mathematical chair in England). He is well known as a popularizer of mathematics, winning two prestigious awards from the Mathematical Association of America for 'outstanding expository writing'. Previous publications include Mathematics and Music: From Pythagoras to Fractals and Sherlock Holmes in Babylon and Other Tales of Mathematical History. Raymond Flood is Emeritus Fellow of Kellogg College, Oxford, having been Vice-President of the college and former President of he British Society for the History of Mathematics before retiring in 2010. He enjoys communicating mathematics and its history to non-specialist audiences, as he has done previously on BBC Radio 4's In Our Time. Previous publications include James Clerk Maxwell: Perspectives on his Life and Work and Mathematics in Victorian Britain.