A series about the animals who have changed the face of the planet and influenced human affairs through their close relationship with people. 2: Rats. In a city at ground level you are never more than a few metres from a rat. Brian Leith investigates these animals which have changed human history by carrying bubonic plague and are now threatening entire habitats on the islands where people unwittingly took them. E-MAIL: nature@bbc.co.uk. Producer Jan Castle