Supermarket Secrets is going behind the scenes again to reveal how the supermarkets are using the latest technology and science to bring us our food. This time, in an age when we expect everything delivered in an instant, how the supermarkets are working to bring us our food on demand. Gregg sees how Ocado are using robots to revolutionise online delivery and visits a state-of-the art lettuce farm in Norfolk where they supply 300 million lettuces per year exactly when we want them. Meanwhile, Nikki tests out the Co-op’s new pay-in-the-aisle technology as we move towards a checkout-free future.