The seizure of the Stena Impero tanker in the Strait of Hormuz is the latest episode to contribute to rising tensions between the UK, US and Iran in the region.
Here is a timeline of recent incidents involving the three nations:
– June 13: Two US oil tankers near the Strait of Hormuz were attacked in an assault that left one ablaze and adrift, with 44 sailors evacuated from both vessels. The US Navy went to assist, with US President Donald Trump blaming Iran for the incidents.
Iran denied involvement in the tanker attacks and accused the US of promoting an “Iranophobic” campaign.
– June 20: A US military drone worth 100 million US dollars (£78 million) was downed by Tehran, with Iran’s president Hassan Rouhani claiming it had violated their airspace.
The move marked a new high in the rising tensions between the two countries, as Iran’s naval commander warned his forces would not hesitate to down more US drones if they entered its airspace.
Mr Trump then pulled back from the brink of retaliatory military strikes on Iran after he was told 150 people could die.
He has since signed an executive order targeting Iran’s supreme leader Ali Khamenei and his associates with financial sanctions.
– July 4: Royal Marines from 42 Commando were involved in an operation to seize a supertanker off Gibraltar suspected of carrying oil destined for Bashar Assad’s Syrian regime. They boarded the ship by descending on ropes from a Wildcat helicopter and by using rigid inflatable boats.
They worked alongside authorities in Gibraltar to detain the Iranian tanker Grace 1, which was believed to be heading to the Banyas refinery in breach of EU sanctions. In response, Iran’s revolutionary guard warned a British oil tanker could be seized in retaliation.
– July 10: Royal Navy frigate HMS Montrose drove off three Iranian vessels which tried to stop the commercial ship British Heritage.
It is understood the tanker was making passage out of the Gulf through the Strait of Hormuz when the ship was approached by the Iranian vessels. HMS Montrose was nearby and proceeded to come in between.
Warnings were given but no shots were fired. The Iranian vessels then turned around and left.
– July 11: Police in Gibraltar said they had arrested the captain and chief officer of the Iranian supertanker Grace 1 in relation to suspected violations of EU sanctions on Syria.
Two days later the force said the captain, chief officer and two second officers of the vessel had been conditionally bailed without charge.
– July 13: In a telephone call with Iranian foreign minister Mohammad Javad Zarif, Foreign Secretary Jeremy Hunt offered to facilitate Grace 1’s release in return for guarantees from Tehran that it would not breach EU sanctions on the Assad regime in Syria.
– July 15: Mr Hunt attended a Brussels meeting of EU foreign ministers on the issue of the Iran nuclear deal.
Mr Hunt said there was a “small window” of hope for preventing the international agreement, aimed at stopping Tehran gaining nuclear weapons, from unravelling.
Both he and Tory leadership rival Boris Johnson later ruled out supporting Mr Trump should he pursue military action in the Gulf.
– July 16: Ali Khamenei called the seizure of the Grace 1 tanker “piracy” and vowed to retaliate.
He said: “God willing, the Islamic Republic and its committed forces will not leave this evilness without a response.”
– July 17: US officials said they suspected Iran had seized a Panamanian-flagged oil tanker from the United Arab Emirates as it travelled through the Strait of Hormuz.
The tanker had turned off its tracker three days before as it entered Iranian waters.
Iran later said its Revolutionary Guard had seized a foreign oil tanker and its crew of 12 for smuggling fuel out of the country.
– July 18: Mr Trump said the USS Boxer had shot down an Iranian drone that came within 1,000 yards of the warship and ignored calls to stand down.
Iranian military officials denied one of its drones had been lost in the Strait of Hormuz.
– July 19: Two oil tankers are reported to have been seized by Iranian authorities in the Persian Gulf.
The Stena Impero, registered in the UK, was seized by the Iranian Revolutionary Guard in the Strait of Hormuz for “violating international maritime rules”, the semi-official Fars news agency said.
A second oil tanker, the Liberia-flagged Mesdar, managed by Glasgow-based firm Norbulk Shipping UK, appeared to veer off course towards the Iranian coast.
The Mesdar’s operator said the ship was boarded by armed guards but the crew were left “safe and well” and allowed to continue their voyage.
Jeremy Hunt called the ships’ seizure “unacceptable” and attended a meeting of the Government’s emergency committee Cobra.