BRIAN: Stock markets around the world tumbled today - as the fourth biggest investment bank in the US - Lehmann Brothers - filed for bankruptcy protection. It's the latest collapse in a long-running financial crisis. The Federal Reserve says it will pump 70 Billion dollars into the markets to ensure liquidity. For more details, let's go straight to Peter at the business desk... PETER: The shockwaves are making themselves felt on this side of the Atlantic in a big way. They're also being fueled by new reports that the US insurer, American International Group, or AIG, has asked the Federal Reserve for help. At the epicentre of it all is Wall Street and a steep fall in American stock values.