At the latest count, sovereign wealth funds from rich oil-producing Middle East countries have invested about $18bn in Europe and the US during the past four months. You can hardly blame them. They are simply taking advantage of an extraordinary window of opportunity to pick up assets in the old industrialised world at bargain prices.

Some of the first of these funds to jump in the market and acquire large stakes in troubled subprime-hit banks may be thinking that they should have perhaps waited a little longer. The shares of their targets – Citigroup, UBS and others – have continued to fall. Had they held back their initial enthusiasm, they would now be able to acquire these same assets at even more attractive prices. But then all these funds are investing for the longer term, or for more arcane reasons that are increasingly worrying western governments.