Inhabitants of Boston are used to rain, given the city’s location towards the northern end of the US Atlantic coast. But even they must have had enough of the cloud that began gathering over State Street Global Advisors, a resident that is also the world’s joint largest asset manager, with the onset of the sub-prime mortgage crisis 18 months ago. It has, if anything, just got darker.

An exceptional writedown of $450m (€351m) at Boston-based SSgA was the largest element of a package of losses announced by its parent State Street last month.