Can we really have witnessed the demise of three top investment banks in so short a time? Bears Stearns, Lehman Brothers and Merrill Lynch have all disappeared off the radar in quick succession.

What is happening to the world’s — and especially the American’s — financial system?

It started with the slicing, dicing and splicing of U.S. mortgages of sub-prime customers. The structured financial instruments that were sold off around the world became known as CDOs (Collateralized Debt Obligations).

They have poisoned the world’s financial system, like seeping toxic waste. Now a new danger is forming on the horizon.

CDSs (Credit Default Swaps — insurance policies for bonded commercial IOUs), which are out there in their trillions and trillions, are beginning to crumble in the face of massive defaults.

The world’s biggest insurer AIG is already in Lehman territory — its shares plummeted by 70 percent in early trading yesterday. The long-foretold CDS crisis is with us at last.

So what precisely are CDSs and how will their demise affect most of us in coming days, weeks, months and years?

George Soros estimates that the value of CDSs now equals half of U.S. household wealth, an almost unimaginable number — let’s call it $23 trillion.

CDSs are hedges made by investors in case a company defaults on its debts. In effect you bet on a company failing to protect your investment in the event it does just that. The problem arises when large numbers of companies go bust and the CDSs themselves become worthless since no-one can pay them out.

A CDS seller undertakes to compensate a buyer if a corporate bond defaults. Since there is no limit to the size of cover taken out, the value of CDSs often exceeds a company’s debts. Moreover, many CDSs are bought with borrowed money so the infection of the system drives deep into the financial heartland like veins in a blue cheese.

The danger now is debt deflation: a rapid reversal of debt issuance, or deleveraging as it is called.

Tim Congdon of the London School of Economics says, “Banking system capital is being wiped out. The risk is that this could lead to a contraction of credit and set off a self-reinforcing downward spiral, leading to the sort of debt-deflation we saw in the 1930s.

“It is already clear that money growth has ground to a halt over the past three months. We must prevent it from actually contracting. If the Fed and European Central Bank don’t cut interest rates soon, it is going to be a problem.”

The Bank of England’s rigid inflation target, set by Gordon Brown when inflation was low, is now a millstone round Mervyn King’s neck at a time when energy, food and commodity price rises are being imported from global markets.

The Eurozone is similarly caught in a time warp relating to Germany’s neurotic fear of hyperinflation. Add the growing divergence between euro economies and a far deeper than necessary downturn is guaranteed for Western European countries.

America is already suffering a double blow: the fading of the effect from the summer tax stimulus and a loss of export competitiveness as the dollar rises.

What began as bad government, worse regulation, grasping banks, financial structures that lacked resilience because they were built on sand, have left us with a perfect storm that is about to come ashore and swallow large parts of the economy.

Yesterday the U.S. Treasury Secretary, Henry Paulson, nationalized the underwriters of half of America’s vast mortgage industry, now in precipitate decline.

Secretary Henry Paulson at news conference yesterday

Two government-sponsored enterprises (GSEs), Fannie Mae and Freddie Mac, have had their books underwritten in the short term by the Government.

Fannie and Freddie are curious institutions. They don’t lend money but underwrite half of U.S. mortgage lending. This amounts to a staggering $5.2 trillion (£2,940 billion) of debt. The two companies are a kind of buffer zone between mortgagees and the real world of finance.

Since the Great Depression, the Government has tacitly made it known that it will support Fannie and Freddie through any adversity. Now that wink has become explicit — until the end of 2009.

So the managers of these enterprises are out, and the shareholders are sent to the dogs, losing 79.9 percent of their holdings to the Treasury. The bondholders — most central banks and commercial banks around the world — are safe, by Government decree. The alternative would have been a liquidation of dollar holdings on an unimaginable scale.

Predictably, bank shares have risen sharply around the world, while the dollar has lost some of its recent glitter in the markets, reflecting the new self-imposed straitjacket binding the Government’s hands for the foreseeable future.

Henry Paulson explained the thinking behind the move. “Fannie Mae and Freddie Mac securities are held by central banks and investors around the world. Investors have purchased securities of these enterprises in part because the ambiguities in their congressional charters created a perception of government backing. Because the U.S. Government created these ambiguities, we have a responsibility to both avert and ultimately address the systemic risk now posed by the scale and breadth of the holdings of GSE debt and mortgage-backed securities.”

He has also committed the Treasury to pumping up to $100 billion into each of the GSEs in the event that their capital ratios fall short.

Fannie and Freddie will now be able “moderately” to increase their lending.

Mark Hake, an analyst at Merrill Lynch, says the British housing market could take 20 years to recover from its current downturn.

Merrill, one of the City of London’s leading investment banks, said, in a note to clients, ” … it looks significantly worse [than the 1990 downturn], with house prices falling faster and further and very little recovery in real terms expected over 20 years. … House prices are expected to be below their August 2007 peak in a further 10 years’ time.”

The bank forecasts house prices to fall by as much as 17 per cent this year, while inflation is set to continue its upward march in coming months as the economy absorbs the effects of higher oil and food prices.

To add to the woes, David Kern, economic advisor to the British Chambers of Commerce, thinks unemployment will rise to nearly two million by the end of 2009. He commented, “The results of this survey signal a menacing deterioration in UK prospects We are now facing serious risks of recession. London appears pretty weak and it’s across the board. Businesses are in a lose-lose situation. Falling demand and the squeeze on consumer disposable incomes will limit how far prices can be increased.”