Ever since the dinosaurs died out over 65 million years ago our planet has been dominated by mammals. A succession of bizarre evolutionary experimental species have come and gone - from walking whales to sabre-toothed cats - yet many of these magnificent creatures have never been visualised. Here, for the first time, some of these spectacular, unfamiliar animals are recreated and set into the context of their world. Walking with Beasts vividly reveals the extraordinary ancestors of modern mammals. Crazy CGI magic courtesy of the BBC.