Mystery in the Mud

S1, E1: In 2002, an astonishing vessel was found in the mud of the River Usk in Wales. Buried for more than 500 years, it was the world's best-preserved 15th Century ship. But a mystery hangs over her, one which science could help solve. Journalist Sean Fletcher investigates the story behind the shipwreck and its discovery. What can it tell us about the Medieval world?