Could be a big day tomorrow:

The US authorities tonight appeared to be preparing the ground for the collapse of Lehman Brothers by sanctioning emergency trading in the Wall Street firm's most complex financial positions.

In an attempt to reduce the risk to the financial system should the fourth biggest firm on Wall Street file for bankruptcy, rival banks with positions in credit, equity, interest rates, foreign exchange and commodity contracts were allowed to trade in a two hour window even though the US financial markets were shut.

If Lehman goes bust it will be one of the biggest failures in Wall Street history...

By allowing trading between the big investment houses tonight, the authorities are hoping to mitigate the impact of a collapse of Lehman on the rest of the financial system. The trading session is predicated upon Lehman Brothers filing for bankruptcy by midnight New York time....

Alan Greenspan, the respected former chairman of the Fed , yesterday warned that other large big institutions could yet be vulnerable....

Greenspan described the credit crisis as a "once-in-a-century" type of event. "There's no question that this is in the process of outstripping anything I've seen and it still is not resolved and it still has a way to go," he told ABC News.