The penny, or whatever currency has just been rigged, may finally have dropped. Prime responsibility for rigging the foreign exchange markets rests with the coterie of dealers who were directly involved. But no one emerges unblemished.

Professional traders smart enough to have worked their way into top positions at some of the world’s leading financial institutions were perfectly capable of understanding that fixing the fix was wrong. It was a benchmark on which many other financial valuations were struck, making the need for probity obvious to all market professionals. Ignorance is not a credible excuse.

But if the dealers involved must take most of the blame, the Financial Conduct Authority is right to criticise the traders’ managers. The chain of command on trading floors runs up from senior dealers to desk heads, departmental managers and all the way up to the board. Front line controls are supplemented by oversight from risk managers and compliance officers. For all three lines of defence to have failed, in so many institutions, for so long, suggests an indigenous bias to optimism among those in charge: this was a systemic collapse of good judgment.