Archaeologist Ben Robinson investigates how Cornish village St Agnes became a world-famous centre of tin mining, where people made and lost huge fortunes. In the bay, the archaeologist unravels the story behind the hundreds of huge carved stones that lie scattered in the surf. There's a look at some medieval technology in action at one of the oldest tin refineries in Britain and a doctor consults his ancestor's 150-year-old medical diary for evidence of past ailments