The board of UBS has put its own interests above those of investors. In accepting the resignation of chief executive Oswald Grübel following the bank’s revelation of a $2.3bn unauthorised trading loss, the board gave in to the gallery of public opinion. By losing its nerve at the critical moment, it has lost the man most able to steer the Swiss bank back on course (again), and, in doing so, created unwelcome uncertainty. Mr Grübel accepted from the outset that the buck stopped with him, but he was expected to stand down only once stability had been restored.

The bank has inserted Sergio Ermotti as a stopgap until it can decide on a permanent successor. In his past two roles, at UniCredit and Merrill Lynch, Mr Ermotti has played second fiddle. He joined UBS only in April, so at least represents an injection of new blood much as Mr Grübel did in 2009. But he will be the fourth chief executive in four years at UBS and will be seen as a temporary appointee. UBS staff knew where they stood under Mr Grübel’s tough stewardship, and were fully aware of his priorities. With the flinty former Bundesbank president Axel Weber waiting in the wings to become chairman from 2013, UBS faces a leadership vacuum at the moment when it most urgently needs significant restructuring.

The greatest problem facing UBS is existential. After its colossal subprime losses and its tangle with US tax authorities, the trading setback has put it back to where it was when Mr Grübel arrived. The bank’s next permanent chief executive will need to act swiftly to turn it into a client-focused, capital-efficient, proprietary trading-free zone. Mr Grübel was best placed to achieve those goals. The blow of his departure will be all the greater if it does not result in staff embracing his example of taking “full responsibility for what occurs at UBS”. Only then will investors’ interests have been served by his resignation.