Lincoln is one of the most historic settlements in Britain: from being the site of a key legionary fort in Roman times to its towering cathedral being the first landmark British bomber crews would see upon their return from daring raids over Nazi-occupied Europe during World War Two. At Lincoln's beating heart is its Castle, strategically situated on top of the central hill that overlooks the Trent Valley. It was constructed by William the Conqueror in the immediate aftermath of the Norman Conquest and is one of only two castles in Britain that has a double motte, making it almost unique. At least twice in its long history, Lincoln Castle has acted as an impregnable bastion: in 1141 the Empress Matilda defeated her cousin King Stephen at Lincoln, during the bloody civil war known as The Anarchy. Meanwhile 76 years later England's most famous Plantagenet knight, William the Marshall, defeated a French invasion force outside the walls of this fortress. In this episode Dan visits Lincoln