Historian Ruth Goodman and archaeologists Peter Ginn and Tom Pinfold turn the clock back to learn the skills of the medieval castle builders by joining the largest archaeological experiment in the world. Although Britain has some of the finest remaining castles of the medieval period, many of their secrets have been lost in time. The origins of our castles are French, introduced to Britain at the time of the Norman Conquest of 1066. So Ruth, Peter and Tom have travelled to Guedelon, in the Burgundy region of France, where an ambitious project is under way to build a medieval castle from scratch, using only the materials and tools available in the thirteenth century.