Was letting Lehman go down the biggest mistake of the crisis? Many, including George Soros in the Financial Times, have argued that letting Lehman go down sowed panic to markets, consumers and businesses.

Not so fast, says Harvard historian Niall Ferguson, in an interview in Davos:

"My position is this is a typical error of historical understanding in which a single event is blamed for much more than it can possibly have caused. You can say ‘Hank Paulson is to blame for my troubles' and if you can change one thing in the story it would have a happy ending.

It's like saying if only Princip had not shot the Archduke Franz Ferdinand in 1914 there wouldn't have been a First World War.

If you go through the events of September of last year you will find it incredibly hard to produce a counterfactual scenario in which it could have been possible to save both Merrill Lynch and Lehman. There is one bank which could be bought by Bank of America but there couldn't have been two.

This is a crisis of too much bank leverage which began in August of 2007 and indeed had it roots far before. A bank leveraged 25-1 only needs a 4 percent decline in their assets to have their equity wiped out. And the notion that saving one investment bank could somehow have prevented or mitigated the crisis is a fantasy. The problem would have happened at some point somewhere else. There is a fundamental problem of bank solvency."