On July 19th the British-flagged tanker Stena Impero sailing in Omani waters through the Hormuz Strait was captured by the Iranian Revolutionary Guards. The move came nearly two weeks after British Royal Marines Commandos seized an Iranian supertanker, near Gibraltar, believed to be carrying oil to Syria in contravention of European Union sanctions.

Britain responded by advising all British-flagged shipping to avoid the Strait. It also dispatched HMS Duncan, a Type 45 guided-missile destroyer, in the area (to replace HMS Montrose), and tasked it with protecting navigation through the Strait.

HMS Duncan is outfitted with Harpoon missiles that give it significant anti-ship capabilities. These could come handy in case Iranian vessels attempt another seizure of British or European ships. Moreover, HMS Duncan carries a contingent of Royal Marines and can also accommodate further forces in the form of Special Boat Service (SBS) operators.

Nevertheless, as former British Foreign Secretary Jeremy Hunt stressed in his speech to the British Parliament, the ship covers an operating area of 19,000 nautical square miles, while the Gulf spans an area of nearly 100,000 nautical square miles. It is thus unrealistic to expect that HMS Duncan will be able to singlehandedly protect traffic.