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. Cherry Healey gets hands-on with the hundreds of workers on a production line in Derbyshire where the millions of chocolate boxes are still surprisingly made by hand. And, Historian Ruth Goodman delves through the chocolate archives to find out what it was like working in the factories before the machines took over.
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