Gregg Wallace discovers how one of Britain's largest bakeries makes up to one and a half million loaves of bread each week. Following the production of one of the nation's favourite loaves, he uncovers the secrets to baking four thousand loaves at once and reveals the incredible machine that can bag a loaf of bread in midair. Cherry Healey goes inside one of the largest flour mills in the country to discover what it takes to make the perfect flour and reveals the secret science to storing bread at home. And historian Ruth Goodman looks at why we've always been in love with the white loaf and shows the hidden killers that used to lurk in our bread.