Hadrian's Wall cut a deep scar across Britain that would never be forgotten. A thousand years after the Romans left, the island split once again, near the line of the wall, into the Kingdoms of England and Scotland. Historian and MP Rory Stewart tells the story of how Britain was torn in two. The border country dividing Britain's lost Middleland became a zone of anarchy, as violent as border areas in the Balkans, Iraq and Afghanistan.