With the G20 summit bearing down on them, both Britain and America are putting their faith in risky strategies in an effort to stablise the domestic, and global, economies. But, as recent history has shown, there’s no such thing as a safe bet in banking, write Heather Stewart and Heather Connon When they meet at the G20 London summit in a month’s time, Gordon Brown and Barack Obama will both be eager to present themselves as the leaders of a worldwide battle to stave off a 21st century Great Depression and clean up the murky depths of the banking sector