Born in Halifax, West Yorkshire, Greg Jackson left school at 16 to write computer games, later joining Greenpeace before returning to study economics at Cambridge. Growing up in a family so stretched that the energy supply was cut off, he channelled that experience into a drive to make energy fairer and more affordable. By his twenties he was running a mirror business, before moving into tech start-up investing. In 2016 he founded Octopus Energy. Less than a decade on, it serves more than 7 million customers in 18 countries, manages a £6 billion renewable portfolio, and licenses its Kraken technology to utilities worldwide — with the company now valued at close to $9 billion.

Producer: Georgiana Tudor