Dinorwig Power Station, otherwise known as Electric Mountain, is a pumped-storage hydro station in Llanberis, Wales. And yes: it's Britain's largest battery. Here's how it works, and why some of the things you think you know about TV pickups might not be so true any more.

Thanks to all the Engie team! More about them: https://www.engie.com/

Camera op: Ryan Priestnall
Editor: Michelle Martin (@mrsmmartin)

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