Hannah Fry takes a look at the bank card. This humble piece of plastic is often taken for granted, but it's the digital key to accessing cash and is packed full of extraordinary technological innovations - including some with surprising and sinister origins.

Hannah is granted the first ever TV access to Visa's European bank card data centre, discovers why we have Russian spies to thank for contactless payments, and finds out how the CIA and a 1950s housewife helped kickstart the bank card revolution.

Hannah Fry delves into the inner workings of virtual assistants, such as Google Assistant and Siri, which are now found in almost half of all UK homes.

Hannah goes behind the scenes with Alexa's chief scientist, reveals how secret technology invented to hunt U-boats led to their targeted hearing, and discovers modern wireless networks' debt to a 1940s Hollywood star.