Credit and lending dried up, many major financial institutions looked vulnerable, and the world economy slipped into a crisis from which it has not yet recovered.
Indeed, the fire-fighting that was needed at that time led to a stressing of government balance sheets and build-up of debt that is the root cause of the second dip of what many now call the Great Recession.
Over these four years, too, the reasons for the crisis have been deconstructed and analysed near-endlessly.
Some of them -- poor regulation, irresponsibility in the financial sector, a lack of understanding of macro-prudential risk -- are now generally accepted as primary causes.
It seems important to ask, therefore, whether these lessons learnt have caused reforms to be implemented.
The answer, unfortunately, seems to be no.
Indeed, the fact is that too little has changed since Lehman fell.
Consider the questions of regulatory reform.
Any hope of closer co-ordination between regulators internationally foundered on the desire of some countries to protect their competitive advantage in lax regulation.
Even within individual countries, the lessons have not been applied.
Regulators dealing with dynamic financial markets cannot always be tied down by legislated rules that are quickly out of date.
Principles-based regulation does a lot better than rules-based legislation.
Yet in the United States' landmark legislative response, the Dodd-Frank Act, started with 'only' 848 pages, has now exploded, with its rules, into being nearly 9,000 pages.
Then there's the question of regulatory co-ordination, necessary to stop financial firms from shopping around for the most
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