On 23 June, Britain was hit by a political earthquake. Within hours of the EU referendum result, the Prime Minister had resigned, the pound fell and Westminster was reeling. So how and why did this political revolution happen - and how does it stand to reshape Britain's politics? In this film, the BBC's Political Editor Laura Kuenssberg tells the inside story of how David Cameron’s huge political gamble went wrong. Talking to the politicians and the people who ran the campaigns, she'll find out how a perfect storm brewed, which would end Cameron’s premiership and throw the Labour Party into chaos, as well as reshaping Britain's place in the world for a generation. In Sunderland - an area where the result sent Britain's political classes into shock - voters, politicians and activists will describe how the groundswell of protest grew. And Laura will explore how a gulf opened up between Westminster and large parts of modern Britain. Just weeks on from the referendum, British politics is already transformed: we have a new Prime Minister, Nigel Farage has bowed out, and Jeremy Corbyn's opponents within Labour have moved against him. But that is just the beginning: the effects of this result will be felt for decades. This film tells the inside story of how it happened.