Even mushroom clouds have a silver lining, and as investors survey the wreckage of Bank of America and Citigroup they can at least see a glimmer of positive news. Citigroup is going to overhaul its board of directors. About time too.

A year ago, this column argued that Citigroup's board of directors represented all that was wrong with governance in the US and in the financial sector, and called on them to take a moral stand and resign.