Iran arrested the UK ambassador for attending a vigil for crash victims Anti-UK protesters outside the British embassy in Tehran on January 12, 2020. Atta Kenare/AFP/Getty Images He was released, but the UK still wants answers. Having come to the brink of war with the US last week and facing anti-regime protests at home, Iran apparently decided it didn’t have enough to deal with and has now picked a fight — with the United Kingdom. On Saturday, Iranian authorities arrested the UK’s ambassador to the country and accused him of participating in the anti-government demonstrations over the downing of the Ukrainian airliner. The ambassador, Rob Macaire, denied that the allegation, saying he attended what he believed was a vigil to honor the victims of the crash, which included at least four people with ties to Britain. ”Normal to want to pay respects- some of victims were British,” Macaire wrote on Twitter. ”I left after 5 mins, when someone started chanting.” 2/2 Detained half an hour after leaving the area. Arresting diplomats is of course illegal, in all countries. See comments by Foreign Secretary @DominicRaab. https://t.co/djpr99iSwI— Rob Macaire (@HMATehran) January 12, 2020 Macaire said he was detained half an hour after leaving the vigil, and the BBC reports he was held before about three hours before he was released. Iranian officials said Macaire was arrested as an ”unknown foreigner” at an illegal gathering, but was released as soon as officials were aware of his identity. The Vienna Convention, which dictates how governments are supposed to treat foreign diplomats and embassies in their countries, broadly gives diplomats immunity from arrest. ”As the Iranian high official has formally announced, the moment the police has been informed of the indentity of the UK Ambassador, he has been freed,” Iran’s ambassador to the UK wrote on Twitter. Still, Iran’s foreign ministry said Sunday it had summoned Macaire to explain his ”illegal and inappropriate presence,” according to the Guardian. And a small group of anti-British protesters — believed to represent the Basij militia, which is connected to Iran’s Islamic Revolutionary Guard Corps — gathered outside the embassy in Tehran, calling for it to shut down. The British government strongly condemned the detention of Macaire. ”The arrest of our Ambassador in Tehran without grounds or explanation is a flagrant violation of international law,” UK Foreign Secretary Dominic Raab said in a statement this weekend. ”The Iranian government is at a cross-roads moment. It can continue its march towards pariah status with all the political and economic isolation that entails, or take steps to deescalate tensions and engage in a diplomatic path forwards.” Prime Minister Boris Johnson has also criticized the arrest for violating international law, and was backed up by his European allies, including German Chancellor Angela Merkel. ”We are seeking full assurances from the Iranian government that this will never happen again,” a spokesperson for Johnson’s office said, adding that the UK’s Foreign Office has ”summoned the Iranian ambassador to convey our strong objections.” This UK-Iran diplomatic spat shows that it’s impossible to isolate the US-Iran conflict This diplomatic back-and-forth might seem quaint compared to what’s going on between the United States and Iran right now, but it reveals how the tensions between Washington and Tehran have rippled out to impact allies. Prime Minister Boris Johnson was, at first, noticeably quiet about the US attack on Soleimani, sending his defense minister to brief Parliament instead. When finally forced to answer questions about it last Wednesday, the prime minister said it wasn’t up to the UK to determine the legality of the strike, as that was the US’s decision, but that Soleimani clearly backed and supported terrorist regimes and threatened civilians. ”That man had the blood of British troops on his hands,” Johnson told British lawmakers on Wednesday. ”That man had the blood of British troops on his hands.”Boris Johnson responds to Jeremy Corbyn’s request for evidence that the killing of Iranian General Qassem Soleimani ”was not an illegal act by the United States.” pic.twitter.com/vi2K25pxR1— Channel 4 News (@Channel4News) January 8, 2020 Still, the UK has urged Washington and Tehran to ease tensions, and it’s continued to try to lobby the US to come back to the 2015 Iran nuclear deal. President Trump said last week that he wanted to scrap the deal entirely, and he urged America’s allies and the other signatories to the deal, China and Russia, to back him. ”The time has come for the United Kingdom, Germany, France, Russia, and China to.. break away from the remnants of the Iran deal or JCPOA, and we must all work together toward making a deal with Iran that makes the world a safer and more peaceful place,” the president said in a speech last week. The UK, along with France and Germany, has been trying to salvage the Obama-era agreement since the US pulled out in 2018, but with little success. The Trump administration’s maximum pressure campaign and the heightened US-Iran tensions after Soleimani’s death make this prospect look bleaker than ever. Iran had already been backing away from some of the commitments in the nuclear deal, and after the strike on Soleimani, it said it would no longer adhere to the limits set in the deal. Trump, of course, has a personal affinity for Boris Johnson that he doesn’t have with Merkel or frenemy French President Emmanuel Macron, but it remains to be seen if the UK prime minister will have success where the others did not. Trump is pretty unpopular in the UK, and Johnson is carefully trying to navigate the relationship with Trump in the hopes of signing a post-Brexit trade deal with the US. This is also a test for the UK’s foreign policy after Brexit. Raab, the foreign secretary, said last week that the UK will introduce a new sanctions regime post-Brexit to crack down on human rights abuses along with the US and Canada, mentioning North Korea and Libya, claiming that the UK’s departure from the EU will give it more freedom to act. But right now, the UK and its European allies have kept, at least publicly, a united front on Iran. The question is whether that will change, especially with this UK-Iran diplomatic dispute.