Over a billion years ago gravitational waves from two colliding black holes started on their journey towards Earth. A century ago Albert Einstein predicted their existence. Then he changed his mind. Then he changed his mind again. Others joined the argument. Finally, forty years ago evidence that they were real came when a binary neutron star was discovered in our galaxy which was decaying in our orbit in just the fashion Einstein predicted, having emitted gravitational waves 21,000 years ago. Subsequently large detectors were constructed on the Earth, such as LIGO, GEO600 and VIRGO to try to detect gravitational waves. But so difficult was theoretically modelling what they would look like that twenty years ago recent Nobel laureate Kip Thorne made a wager that theorists would still not have predicted their form before the detectors saw them. In 2005 a breakthrough was made in supercomputer simulations of binary black holes so that templates were available just in time when the gravitational waves arrived on Earth two years ago after their billion year journey.