The Western fleet which sailed through the Straits of Hormuz bristled with firepower – a 100,000-ton nuclear powered aircraft carrier, half a dozen escorting warships, a flotilla carrying almost a hundred strike jets and attack helicopters. The exercise in 21st century gunboat diplomacy was a very public message to Tehran that the closure of the waterway vital for oil shipments would not be tolerated. The sanctions imposed by the EU and the US on Iran are being seen as the last chance to resolve the nuclear stand-off before air strikes come into consideration. In the background there is the constant drumbeat from hardliners in Israel and America that continuing military inaction equates to time lost as Mahmoud Ahmedinejad's regime inches its way towards acquiring the bomb.

But, for the time being at least, an economic rather than a shooting war is unfolding. What was more interesting in the reactions from Tehran to the EU sanctions was not yet another threat to shut down Hormuz, a military gamble too costly for the Iranians and one, even if it succeeded briefly, that would have the effect of blocking its own oil exports. Much more significant was the statement by former intelligence minister Ali Fallahian and other senior figures that Iran should retaliate first and immediately switch off oil supplies to the EU.

This, if mechanics allowed, would be far from an empty gesture. The EU is acutely aware that the member states most dependant on Iranian oil – Greece, Italy, Spain – are the most stricken by the eurozone crisis.

That is the reason a review mechanism of around six months had been built into the sanctions system to allow these countries to find alternative supplies and prepare for additional costs.