British tanker seizure is a menacing provocation

All countries must de-escalate tensions in the Gulf and defend freedom of navigation

The British oil tanker Stena Impero has been captured by Iran. AP

With Iran's seizure of the British Stens Impero tanker in the Strait of Hormuz, we are now just one mistake away from a serious confrontation. In spite of the Iranian foreign minister Javad Zarif's recent assertions that Tehran is prepared to negotiate with the US, the regime has decided to further escalate a perilous situation – vindicating the Trump administration's strategy of maximum pressure.

This is the second time in just over a week that the UK has been the target of escalatory violence, after Iranian boats tried to impede a British oil tanker in busy international waters, before being warned off by a royal navy ship. Both incidents follow the seizure of an Iranian vessel carrying oil to Syria, in violation of EU sanctions, off the coast of Gibraltar.

Alongside France and Germany, Britain has been trying to salvage the 2015 Iran nuclear deal after US President Donald Trump withdrew last year. With attacks on British vessels, Iranian foreign policy looks increasingly rash and erratic. That is why all countries must endeavour to de-escalate tensions in the Gulf, and defend freedom of navigation.

However, while only diplomacy can avert war, Iran must be reminded that raids on commercial vessels will not be tolerated. Put simply, this cannot become the new normal.

Just days away from welcoming a new prime minister into Downing Street, and still committed to the nuclear deal, perhaps Britain is viewed as an easy target. In a measured statement, UK foreign minister Jeremy Hunt expressed deep concern about this "unacceptable" seizure, and promised "serious consequences" if the situation is not quickly resolved.

The incident came just one day after Mr Trump vowed to “aggressively” defend vessels in the Gulf. Tehran knows it is no military match for the US and UK, and yet, as this case makes clear, it is now pursuing a strategy of escalatory tanker attacks.

The US is working on a multinational maritime effort to increase surveillance of, and security in, the vital waterways of the Gulf. Still, it is worth asking why the British-flagged Stena Impero was allowed to sail, unprotected, through the Strait of Hormuz, following a series of threats by Iran against British vessels. Individual nations have a responsibility to protect and escort their ships, to ensure Iran is denied small victories of this kind. Meanwhile, shipping companies have been urged to avoid hiring private armed security for their ships, as the world tries to avert a serious escalation.

Picking a fight with Britain will not help Iran in the long run, but that does not seem to matter to hardliners in Tehran. That is what makes them so dangerous. The international community must defuse the situation, seek the tanker’s return, and remind Iran that attacks of this kind will not be tolerated.