Standard Chartered, a British bank, has found itself on the receiving end of a bluntly worded message: do business with Iran, and the US will punish you for it. Executives at the bank are not the only ones wondering: “Who are these Americans to penalise a British bank for doing business with a third country? What gives Washington the right to strong arm European regulators into supporting US foreign policy plans?” The answer: the same Americans who do not want to see Iran develop a nuclear weapons capability but who are not prepared to provoke another Middle Eastern war by dropping bombs to destroy it.

For the past several years, market anxiety over Iran has focused on the risk of military strikes on the country’s nuclear programme. When will Benjamin Netanyahu, Israeli prime minister, give the order to drop the bombs? Will Barack Obama help? Will Iran block the Strait of Hormuz, the bottleneck through which about 40 per cent of the world’s seaborne crude oil passes each day? Are we heading towards another war in the world’s most volatile region?

As Standard Charteredhas learnt the hard way, military conflict, even a limited one, is not the likeliest market-moving Iran-related risk. Sanctions are not simply the opening act to a more dangerous moment, Iran’s equivalent of the shortlived Kofi Annan mission to Syria. Sanctions are the headline risk.