Sceptics are understandably driven in their judgment by the unlikely expectation that sanctions would disrupt Iran's nuclear programme's supply lines to the point of stopping it or getting the regime to negotiate. Instead, as the song goes, they are killing Iran's regime softly within, by crippling its financial system and preventing the regime from banking on its energy resources.

If this continues, well before Iran can assemble its nuclear weapon, its economy will collapse. The ensuing social pandemonium is the last thing the regime can afford-which is why a further tightening of sanctions is the best bet for a compromise before Iran has the bomb. Otherwise someone will sooner or later conclude it is time to stop Iran by more drastic means.