From BBC Panorama. Three years ago, Britain had a new Prime Minister and a promise to take the United Kingdom out of the European Union by delivering on the people's vote for "Brexit". What had been presented as a simple proposition - for the UK to leave - has turned into a political nightmare, dividing former allies, British political parties and the people of an increasingly dis-United Kingdom. Now Britain's new PM, Boris Johnson, is making bold promises to "leave". In this revealing account, key negotiators and politicians on both sides of the Channel tell the inside story of the Brexit debacle.