Stena Impero seized in Strait of Hormu​z on Friday night

A second tanker, Mesdar, was stopped before being released

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Two British oil tankers were seized by Iran’s Revolutionary Guards in the Strait of Hormuz on Friday night, in a major escalation of tensions in the Gulf.

The British-flagged Stena Impero had been en route to Saudi Arabia, but abruptly changed course and began sailing towards the Iranian island of Qeshm, data relayed by maritime tracking services showed.

The 30,000-tonne ship “went dark”, meaning its transponder was turned off, at 4.29pm UK time and nothing has been heard from her or her 23 crew since.

A second oil tanker, the British-operated, Liberian-flagged Mesdar, was intercepted by the Guards about 40 minutes after the course shift by Stena Impero, and was held for some time before being allowed to resume navigation.

HMS Montrose, the Type-23 frigate, was understood to have been dispatched to help the Stena, but was minutes too late.

Jeremy Hunt, the Foreign Secretary, said he was “extremely concerned by the seizure of two vessels by Iranian authorities in the Strait of Hormuz”.