Giles Milton visits the key D-Day sites along the Normandy coastline including Omaha Beach and Pegasus Bridge. We hear the stories of the men and women on both the attacking and defensive lines from undercover spies to radio operators to those manning the machine gun nests. We also visit the beach of Morfa Bychan in West Wales to see where the Allies built replica defences for their invading army to do practice runs of the greatest seaborne invasion in history.