JPMorgan Chase’s performance in the crisis gave it and Jamie Dimon, its boss, a claim to being better bankers than their rivals. The beaching of the “London whale”, a trader whose positions have been implicated in a $2bn loss reported by the bank, suggests it had more to do with better luck than greater skill.

The luck has now run out, as it always does in the end. JPMorgan’s shareholders will take the pain. For others the episode should serve as a spur to getting bank regulation right. His bank’s good performance until now has allowed Mr Dimon to push back against ambitious regulatory reform. The argument is that reining in reckless practices to reduce risk should not get in the way of the business models of more prudent bankers.

JPMorgan’s whale-size loss – and Mr Dimon’s original dismissal of it as “a tempest in a teapot” – undermines his case. That “value at risk”, a measure JPMorgan pioneered, failed to flag the impending loss shows how hard it is to keep risk in check, even for the most diligent banker. More fundamentally, the episode brings home that risk is the price for the outsize returns banks now expect. Until banks become more like utilities – predictable businesses with low, stable returns – regular wipeouts of profits will be the rule.