Gregg Wallace is inside one of the world's largest chocolate factories in York to discover how they produce a staggering seven million bars a day. He'll follow the incredible 24-hour journey - from bean to bar - of one of our best-selling chocolates and meet the team of people who work around the clock to keep up with that demand.Cherry Healey gets hands on with the hundreds of workers on a production line in Derbyshire where the millions of chocolate boxes they produce every year are still surprisingly handmade.Historian Ruth Goodman delves through the chocolate archives to find out what it was like working in the factories before the machines took over, and she meets the people who found love on the production line.