Iran’s apparent ease in targeting British-linked shipping in the Arabian Gulf has raised concerns in London over an absence of leadership at the top of government. News that the Stena Impero, a British-flagged vessel owned by a Swedish firm, and the Mesdar, a Liberian-flagged tanker owned by a Scottish firm, has rocked Theresa May's outgoing team. Days before Iran’s Supreme Leader Ayatollah Ali Khamenei warned that Britain’s seizure of the supertanker Grace 1 at Gibraltar for sanctions-busting was piracy and this "evil" would not go unpunished. Just hours after a Gibraltar court extended the detention of the tanker, the IRGC scrambled a helicopter and intercepted the two ships, holding the Stena Impero but letting Mesdar go after a warning over "environmental infringements". Leading MPs and former military figures were quick to warn that the incident had painfully exposed Britain. Tom Tugendhat, the Conservative chair of the Commons Foreign Affairs Committee, worried that the protracted race to succeed Mrs May as prime minister was taking its toll. He publicly warned “whoever walks into No 10 [Downing St] on Wednesday the hiatus in power in the UK has gone on too long,” adding that the country was being tested by both its friends and its enemies. “The UK cannot afford to look weak. We must stand up to bullies because the threats only increase if we are not robust against aggression,” he said. In the Arabian Gulf, Britain has been at the eye of a storm for weeks. HMS Montrose, the frigate permanently stationed in Bahrain, was forced to fend off IRGC fast boat aggression as it escorted the BP-owned tanker British Heritage through the Straits of Hormuz ten days ago. According to British officials, the Montrose responded on Friday, changing course and moving at 20 nautical miles to assist the Stena Impero from Oman’s waters but arrived too late to challenge the Iranians as they forced the ship into their own territory. London has announced that the far larger naval destroyer HMS Duncan would travel to the region to reinforce its patrols. HMS Kent, another frigate, has also been tasked to patrol the area but won’t arrive for some time. Lord West, a former head of the British Navy, said on Friday it was too little and too late. He said he was “astonished” that the British-linked vessels in the shipping channels were not getting an escort as a routine. Jeremy Hunt, the foreign secretary, was wrapping up his Conservative leadership bid as the news broke. He attended a late-night Cobra meeting of officials and military chiefs. Afterwards, a statement said the government response would be “considered and robust” and Mr Hunt said Britain was committed to the protection of its shipping. The message from Whitehall was a mixed one. The statement added British ships had been advised to stay clear of Iranian waters for an interim period. Boris Johnson, the favourite to beat Mr Hunt to Mrs May’s job, watched the unfolding events in silence. He was tested and found wanting by Iran when he mishandled the case of Nazanin Zaghari-Ratcliffe. In a rare admission of personal responsibility, he recently conceded he is haunted by her detention in a Tehran prison on spying charges.