"Essential listening..." Why the US and UK went to war in Iraq and its legacy. Gordon Corera investigates.Twenty years ago a US-led coalition invaded Iraq to overthrow Saddam Hussein. The UK was America's main partner. For many it remains a war based on a lie. So why did it happen? Why was Washington so fixed on regime change in Iraq? And why did the British Prime Minister, Tony Blair, commit the UK to taking part? The BBC's security correspondent Gordon Corera seeks to find new answers to why the war happened and what it meant. Gordon speaks to those...