Gregg Wallace is in Lowestoft, at an enormous factory where they produce 450 tonnes of frozen food each day. He follows the production of frozen potato waffles, from the arrival of 25 tonnes of potatoes right through to dispatch. Along the way he discovers how they make a monster amount of mash and marvels at the technology which stamps out a million identical waffles every 24 hours, each weighing 68 grams and exactly 15 mm thick.Meanwhile Cherry Healey is learning about the differences between waxy and floury potatoes and finding out which spud you should use for which job. Small waxy potatoes are best in salads and boiled, while floury potatoes produce the best mash and roasties. She's also asking whether, in these carb-conscious days, we're unfairly demonising the potato. At King's College London she meets a dietician who runs tests which show that the potato, gram for gram, has more vitamin C than beetroot and carrot and more potassium than banana. Keeping hold of these nutrients isn't easy. But Cherry is delighted to discover that skin-on wedges, as long as you go easy on the oil, are a nutritional winner.Historian Ruth Goodman is myth busting Walter Raleigh's connection to potatoes. She discovers that he couldn't have brought them back from North America, because there weren't potatoes there until 20 years after he died. Instead the credit must go to Spanish explorers and an enterprising French chemist called Parmentier, who popularised this exotic new vegetable. She also meets one of the inventors of the potato waffle, who shows her how Mr Whippy ice creams were the inspiration behind this teatime treat.