Amid turmoil in the eurozone, it has been some time since we heard an American voice apologising for a financial disaster. It has been even longer since that voice belonged to Jamie Dimon.

Mr Dimon has been best-known in the past year or two for his punchy, sometimes angry, defences of JPMorgan Chase, the banking group of which he is chairman and chief executive, and of the social value of “too big to fail” banks. The man who used to be the Obama administration’s favourite banker (and a tip for Treasury secretary) has tussled with regulators and berated journalists.

Mr Dimon changed his tune abruptly on Thursday evening, on a hastily convened conference call during which he disclosed a $2bn financial trading loss and ate a great deal of humble pie. The offending trade had been “flawed, complex, volatile, poorly reviewed and poorly monitored?.?.?.?there are many errors, sloppiness and bad judgment”, he said, concluding unhappily: “It plays right into the hands of a bunch of pundits out there.”