Michelin-starred chef Angela Hartnett tackles sell-by dates with the US military, greengrocer Chris B*in heads to Australia to see the world's leading robotic farm, technology expert Shini Somara is in Shanghai, where she's immersed in the restaurant of the future, and Dara is in Britain's largest hi-tech farm to see the secret of growing hundreds of thousands of tonnes of fruit and veg - without any soil.