In 865 AD Britain was invaded by the Great Heathen Army an alliance of Scandanavian warriors determined to conquer the kingdoms of East Anglia, Northumbria, Merica and Wessex. Over the next few years, all of those kingdoms would fall to the Viking forces with the exception of Wessex. In May 878 Alfred the Great defeated the Vikings at the Battle of Edington. However, despite this defeat, the Vikings did not leave, but rather reached an agreement with Alfred allowing them to retain control of much of the north and east of England in what would become known as the Danelaw. Professor Cat Jarman joins Dan as they travel across the country exploring the key sites of the Viking conquest and looking to discover what may still be to discover about the Great Heathen Army.