Iraq's Poisoned Rivers

Two great rivers - the Tigris and the Euphrates - have been the lifeblood of Iraq for centuries. But last summer, toxic water in the southern Iraqi city of Basra sparked an explosion of anger and unrest as tens of thousands of people across the city fell sick. Martin Patience has been on a journey from the mountains of northern Iraq to the southern marshes to investigate the country's environmental catastrophe and trace how Basra has become the epicentre of the crisis.