Every year the UK produces around 50 million tyres for disposal. They are supposed to be sent for recycling. Instead, big money is being made by diverting tyres to illegal and dangerous 'pyrolysis' plants where they are melted down to extract oil and steel. Together with a team of journalists from Source Material, a not-for-profit group specialising in climate and corruption, we follow the tyres from the UK to India using tracking devices. The team discovers just how large scale this largely illicit business has become. Earlier this year, a makeshift pyrolysis plant exploded near Mumbai, killing four people. It had been processing tyres from abroad. Reporter Paul Kenyon confronts a tyre trader in the north of England who admits to shipping his waste tyres to India for pyrolysis.