Could another AIG-style disaster shake the financial markets again? It is not an entirely idle question. This month, there has been plenty of hand-wringing about the anniversary of the Lehman Brothers collapse. But behind the scenes the issue of AIG - and its links to the credit derivatives market - is currently provoking even more debate among some finance officials.

After all, when AIG imploded in September 2008, the potential losses on its credit derivatives contracts were so devastating for the system, because they were so concentrated, that the US government used tens of billions of dollars to honour the deals, benefiting groups such as Goldman Sachs, Société Générale and Barclays. And that money, remember, will not return to the Treasury's purse (unlike the sums invested to boost bank capital, say).

Yet if that is startling, what is more striking is that a well-respected Fitch survey before the collapse of the credit bubble suggested that AIG was just the 20th largest credit default swap player in the sector, based on gross notional outstanding volumes. No wonder those billions of lossmaking contracts subsequently came as such a shock.