In recent days, several of America’s largest investment groups, such as Fidelity and Northern Trust, have been discreetly reviewing their staff holiday plans. The reason? Right now, with the summer heat rising, the mood in the financial markets seems relatively calm.

But the issue worrying some investment firms is what might be called the “summer curse”; precisely because trading volumes tend to be so thin in the summer months, and senior hands are away, markets can go completely haywire if something does go wrong.

And this “summer curse” is not a theoretical issue. Just think of 1998 (the Russian crisis and Long-Term Capital Management hedge fund implosion); 2007 (the mortgage securities and money market freeze); 2008 (the Fannie Mae “jolt”, which led to the Lehman Brothers disaster); or, for that matter, think back to how markets were rocked last year by the eurozone crisis and the US debt ceiling dramas.