The attack did not emerge from nowhere. In November 2011, the International Atomic Energy Agency released a report documenting weaponization elements of Iran's nuclear program. The British government responded by banning all UK financial institutions from doing business with their Iranian counterparts, including Iran's central bank. The sanctions struck at the core of Iran's economy. Tehran retaliated through parliament, approving a bill to downgrade ties with London and requiring both countries to withdraw their ambassadors. The diplomatic temperature had been climbing for weeks. What happened at the embassy was the point at which rhetoric became action.

The question of who orchestrated the attack consumed the aftermath. The demonstrators issued a statement calling their actions "a spontaneous reaction of revolutionary students," insisting no state organ had ordered them. Few observers believed it. Al Jazeera's Tehran correspondent reported that Iranian police and several government ministries had prior knowledge of the protest, which had been organized by the student arm of the Basij, a paramilitary force loyal to the Supreme Leader. The Economist put it bluntly: "This was the centre of the capital city. If the police had wanted to stop this, they could have flooded the compound with officers." Two Iranian opposition student groups, Tahkim Vahdat and Advar Tahkim, condemned the attack and declared that those behind it were "not true representatives of Iranian students" but "affiliated with the authorities in power."

Britain's response was swift and severe. Prime Minister David Cameron called the incursion "outrageous and indefensible." The next day, Foreign Secretary William Hague stood before the House of Commons and announced that the Iranian ambassador and all Iranian diplomatic staff had 48 hours to leave the United Kingdom. He also confirmed that the British Embassy in Tehran had been closed and its staff evacuated. Relations between the two countries dropped to their lowest point in modern memory. France, Germany, Italy, and the Netherlands recalled their ambassadors for consultations. The UN Security Council condemned the attack "in the strongest terms." Canada went further, closing its own embassy in Tehran the following September and expelling all Iranian diplomats from Canadian soil.

Beyond the diplomatic fallout, the attack had immediate human consequences that rarely made headlines. The Ecole Francaise de Tehran, located on British embassy property, was in session when the mob stormed the compound. Children were inside. The German Embassy School, situated near the British compound, had its windows shattered. All three international schools in the area -- the French, German, and British schools -- closed indefinitely. The board of trustees of the British School of Tehran voted to permanently shut the institution, setting December 31, 2011, as its final day. The German school absorbed the British school's assets and opened an international section in its former buildings. Families that had built lives around these institutions had weeks to find alternatives.

Diplomatic recovery took nearly four years. In November 2013, Iran and the UK agreed to appoint non-resident charges d'affaires, a tentative first step. The real breakthrough came in the summer of 2015, when the Joint Comprehensive Plan of Action -- the Iran nuclear deal -- opened a path to broader engagement. In August of that year, Iranian Foreign Minister Mohammad Javad Zarif and British Foreign Secretary Philip Hammond announced the embassy's reopening at a joint press conference in Tehran. Even then, Iranian students protested outside the ceremony. The Sultanate of Oman and Sweden, which had served as protecting powers representing Iranian and British interests respectively during the closure, could finally step aside. The building on Ferdowsi Avenue resumed its function, though the scars of November 29, 2011, had not fully healed.