Biographical note

Alex Bellos writes about maths and puzzles for the Guardian and is the bestselling author of Alex's Adventures in Numberland and Alex Through the Looking-Glass, as well as two mathematical colouring books. He has also written Futebol: The Brazilian Way of Life, which was shortlisted for Sports Book of the Year, and he ghost-wrote Pele's bestselling autobiography. He lives in West London. Ben Lyttleton is a journalist, broadcaster and football consultant. He is the author of Edge and Twelve Yards: The Art and Psychology of the Perfect Penalty and his football articles have been published in over 20 countries. He is a director of Soccernomics, a football consultancy that helps teams improve their performance. He lives in North London.