In the month that followed the bankruptcy of Lehman Brothers in September 2008, the world stared into the abyss of total financial collapse. The third part of the BBC's definitive series on the crash tells the extraordinary story of how politicians reacted, and asks what has been learnt from the entire calamity. Could it happen again? With unrivalled contributions from the key decision makers including US Treasury Secretary Tim Geithner, Gordon Brown and five other finance ministers, the programme pieces together the details of an extraordinary moment in history, when the world faced its greatest financial crisis.