Nature is nothing if not rhythmic, and its rhythms are many and varied. Many of nature’s rhythms are like the heartbeat: they take care of themselves, running ‘in background. Others are like breathing: there is a simple ‘default’ pattern that operates as long as nothing unusual is happening, but there is also a more sophisticated control mechanism that can kick in when necessary and adapt those rhythms to immediate needs. Controllable rhythms of this kind are particularly common – and particularly interesting – in locomotion. And behind it all, inevitably, is mathematics…

Ian Stewart read Mathematics at Churchill College, Cambridge before completing his doctorate at the University of Warwick where he is now a Professor of Maths. He was the first recipient of the Christopher Zeeman medal and has held visiting professorships in the United States, Germany and New Zealand. He has given the Royal Institution Christmas lectures and is a fellow of the Royal Society. He was the Gresham Professor of Geometry between 1994 and 1998.