What can be calculated is surely only the very tip of the iceberg.

The cost of all global bank bailouts after Lehman’s shock bankruptcy filing is a figure that can only be estimated. According to the Bank of England’s Financial Stability Report in October last year, governments and central banks across the world may have to bail out the global financial industry with $4.5 trillion of taxpayers’ money -- some 8% of the $60.7 trillion global economy.

We can also calculate the value that was destroyed when the unplanned bankruptcy forced down prices for Lehman’s assets in a market that was artificially depressed by the collapse.

According to one analysis, by Lehman’s liquidators, the total loss to unsecured creditors was a cool £120bn -- with almost half of that caused by

Lehman’s shamed chief executive Dick Fuld, who rushed the foundering investment bank into a bankruptcy filing.

Most of the loss of value is believed to have occurred because the bankruptcy filing caused the bank to default on trading contracts with counter­parties, cancelling almost a million derivatives contracts. An orderly unwinding might have saved at least £30bn for creditors.

The trauma inflicted by Lehman sent the global economy into a tailspin.

However, the great and vast unknown is the full cost of the firestorm in the global markets that followed the collapse and the financial meltdown that rippled out and continued to wreck hundreds of thousands of livelihoods, slowed consumer demand, saw countless manufacturers close their factory gates and even blew apart the Icelandic economy.

According to an estimate by Steve Schifferes, from City University London, the collapse of Lehman and the ensuing financial whirlwind has cost UK households £31,000 apiece.

In the US, the Treasury Department bought huge chunks of equity in Bank of New York Mellon, Goldman Sachs, JP Morgan, Morgan Stanley, Bank of America, Merrill Lynch, Citigroup, Wells Fargo, State Street and insurance giant AIG, among a raft of others.

Banks are still collapsing. US regulators last week closed a large bank in Illinois in one of the biggest collapses of the year, and two in

Minnesota and Washington, at a cost of more than $2bn.

These latest failures pushed the 2009 American total to 92. The global wave of failures is expected to continue and the cost of the financial tempest will not abate for years to come.

The pain continues to be felt in the Scottish financial sector, with thousands of jobs on the chopping block after Lloyds TSB’s government-driven rescue takeover of HBOS in January and the government bailout of Royal Bank of Scotland. Unemployment across the UK is expected to peak at more than three million.

To be sure, the fall of Lehman did not cause the global economic downturn. Common consensus lays the blame for the worldwide recession squarely at the feet of the US sub-prime

housing market and the bankers who diced and spliced it into complex derivatives, exotic mortgages and sky-high leverage.

Catherine Schenk,

professor of international economic history at Glasgow University, said: “There is no doubt that the Lehman collapse was a precipitating factor that turned a difficult situation in a disastrous one.

“There had already been crises at Northern Rock and Bear Stearns, but the situation in September was levelling out. Then came Lehman and it all went from bad to worse.

“It became clear very quickly that Lehman should have been bailed out. The cost of not bailing it out was the spreading of fear through the global financial system and a world economy that has yet to recover.”

It is fair to say, however, that Lehman was among those dicers and splicers, and that its risky assets and exposure to the sub-prime property crash had been the subject of Wall Street rumour for months.

If we liken the global financial crisis to a kind of explosion, or a serious of related explosions, then

Lehman’s collapse was the detonator for the bigger blasts to come. It precipitated disaster. And the aftershocks of the blast it set off by its own demise and by the US government’s failure to rescue it were far-reaching.

The size of the Lehman detonation was not huge in itself -- bankruptcy with debts of more than £360bn -- but its interconnectedness with so much of the rest of the world’s financial system turned it into a problem of global proportions.

In Europe alone, Lehman Brothers International held more than $30bn of client assets at the time of its collapse. In Hong Kong, some 37,000 investors bought more than £1.2bn of Lehman-related financial products.

The US state of Florida and its citizens lost more than £600m. More than £260m disappeared from the pension fund that pays benefits for a million retirees and public workers. Counties, cities and school districts faced a loss of more than £180m.

Moreover, in the days after Lehman filed for bankruptcy, a £38bn US government money-market fund took a big hit on Lehman’s commercial paper which, in turn, prompted a flood of withdrawal requests.

The US government had to guarantee money-market funds to prevent a run, which would have likely further seized up the already tight credit markets.

There are few certainties in world finance, although most experts are certain that it will be years -- if ever -- before the full cost of the Lehman Brothers collapse can be fully comprehended, let alone calculated.

A full and true reckoning of the collapse of Lehman Brothers is incalculable