As the technology bubble imploded, fund managers stopped pretending to know what ethernet routers did and started asking what life would look like if all tech stocks halved in value. The structured credit market has yet to reach this moment of clarity. As is typical when the sky falls in, many specialists, obsessed with complexity, point to the impossibility of generalising about the weather.

It is true that in terms of the vintage and profile of the underlying collateral, and the priority of claims on it (subordination), a dazzling range of permutations exist for collateralised debt obligations. And the $23bn of subprime write-offs so far from the three banks worst hit suggest intellectual chaos: relative to their remaining exposure to “super- senior” CDOs, UBS wrote down 8 per cent, Merrill Lynch 41 per cent, while Citigroup’s guidance is 19 per cent.