Gregg Wallace is in Essex at an enormous cereal bar factory, which produces 400,000 fruit- and nut-packed treats a day. Gregg follows production from the arrival of two tonnes of macadamia nuts all the way through to dispatch. Along the way, he gets hands on with all the ingredients, from nuts to cranberries and sultanas to puffed rice.

Meanwhile, Cherry Healey is helping out with the macadamia harvest in South Africa. The country is the world's largest producer of these nuts, responsible for a quarter of the global harvest.
Historian Ruth Goodman climbs a mountain in the Lake District to meet an explorer who tells her all about one of Britain's original snack bars, Kendal Mint Cake. Its popularity grew after famous explorers Ernest Shackleton and Sir Edmund Hillary took it on their expeditions to Antarctica and Everest respectively.