How do you apply game theory to select who should be on your Christmas shopping list ? Will calculations show Santa is getting steadily thinner - shimmying up and down chimneys for a whole night - or fatter - as he tucks into a mince pie and a glass of sherry in billions of houses across the world?

You are accused of a crime. Who would you rather determined your fate – a human or an algorithm?
An algorithm is more consistent and less prone to error of judgement. Yet a human can look you in the eye before passing sentence.
Welcome to the age of the algorithm, the story of a not-too-distant future where machines rule supreme, making important decisions – in healthcare, transport, finance, security, what we watch, where we go even who we send to prison. So how much should we rely on them? What kind of future do we want?

Hannah Fry takes us on a tour of the good, the bad and the...