Seizure of Iranian oil tanker off Gibraltar was welcomed by US hawks but left Britain looking vulnerable

When Gibraltar’s authorities unexpectedly impounded the Iranian oil tanker Grace 1 in July, one member of Donald Trump’s administration was particularly pleased. John Bolton, the president’s hawkish national security adviser, tweeted: “Excellent news”.

The authorities in Gibraltar – with the backing of the British – said the vessel was heading for Syria. Selling oil to the regime of Bashar al-Assad was in breach of EU sanctions.

But for the US, the seizure served a wider purpose, first to ratchet up the economic pressure further against Syria and above all Iran. Its cargo, worth $140m (£116m), represented lost revenue for Tehran as well as a lost source of energy for Damascus regime.

Gibraltar says it will free oil tanker at centre of Iran row Read more

Caught up in the middle, however, was Britain. Iran seized a British-flagged tanker in the Gulf in retaliation, under the noses of the stretched Royal Navy, leaving British merchant shipping looking vulnerable in the region, despite UK claims that Gibraltar had acted independently.

Britain needed help in the Gulf and under new prime minister, Boris Johnson, chose to turn to the US, abandoning an idea first aired by his defeated leadership rival Jeremy Hunt, who had wanted to create a European-led naval protection force in the world’s busiest oil shipping lane.

It was a decision British officials tried to play down when it was announced last week that the UK would “join in with” the US on maritime security in its initiative, Operation Sentinel.

But when Bolton came to London on Monday, he was far less subtle. “We were pleased PM Johnson’s government has agreed to participate in Operation Sentinel,” he said, adding pointedly that the move “reflects a change from the prior government”.

Hunt and the former prime minister Theresa May were acutely aware of French and German sensitivities and did not want to throw their naval lot in with the US in waters just south of Iran, at a time when all three European powers want to cool tensions with Tehran and keep the nuclear deal negotiated under the Obama administration alive.

As for the Grace 1 tanker, Iran had given assurances behind the scenes to Gibraltar that, if released, it would not sail to a country subject to EU sanctions such as Syria, meaning that the continuing detention of the ship was becoming increasingly hard to justify.

But with Washington determined to maintain the economic pressure on Iran, the Americans had little choice but to raise the stakes by making a legal challenge to Gibraltar’s decision on Thursday – a policy denounced by Iran’s foreign minister, Mohammad Javad Zarif as “economic terrorism”.

London has acknowledged that the US notified the British authorities of its intentions to try to prevent the release of the Grace 1. But such are the sensitivities, British officials would not say whether Bolton had raised the topic of the tanker in his meeting with Johnson this week, or in any of the other meetings with ministers.

It would be surprising, however, if Bolton had not done so. But in any event, Britain has once again has become increasingly embroiled in the US economic power play with Iran, and if the Grace 1 is further detained, the tanker crisis is far from over.