The big oil companies are the pantomime villains of the global warming debate. They've been accused of everything from climate change denial to commercial incompetence in a rapidly changing world. Campaigners attack their boardroom practices and push pension funds and universities to withdraw their investments.

Tom Heap examines the reactions of the likes of Exxon, Shell, BP and Total to the mounting evidence of man-made climate change. How much did they know? How much did they lobby against meaningful action? He meets Lord Browne, the former head of BP who famously rebranded his company as 'Beyond Petroleum' to find out why the rest of the industry failed to join his campaign to cut emissions and invest in renewable energy.

Tom and Lord Browne also discuss the changing rhetoric since the signing of the 2015 Paris climate change agreement. With fresh commitments to alternative fuels could the oil companies finally turn themselves from the villain to the principal boy, using their engineering expertise to halt the planet's changing climate?

Producer: Alasdair Cross.