Britain's diplomatic presence in Tehran began modestly in 1821, tucked into the crowded lanes of the Old Bazaar. By the 1860s, overcrowding and poor sanitation made the location untenable, and the government purchased land along what is now Ferdowsi Avenue. The architect James Wild -- experienced in Middle Eastern design from his earlier commissions -- was brought in to supervise construction of the new Legation Buildings. Wild's creation, completed in June 1876, blended European institutional architecture with the scale and setting suited to Tehran's climate. The compound grew into a sprawling presence in the heart of the city, its high walls enclosing gardens that would become far more than decorative.

The word bast means sanctuary in Persian, and the concept carried genuine legal and cultural weight. When Mozaffar ad-Din Shah Qajar's government cracked down on reformers demanding a constitution, thousands of Tehranis exercised this ancient right by flooding the British compound in July and August 1906. The numbers were staggering -- as many as sixteen thousand people packed the grounds. Markets closed. The city's commercial life ceased. Under this extraordinary pressure, the shah capitulated. On August 5, 1906, he issued a farman granting Iran its first constitution and establishing a National Assembly. The constitutional revolution had found its turning point not on a battlefield but in the gardens of a foreign embassy, where the act of simply refusing to leave proved more powerful than arms.

The embassy's modern history reads like a seismograph of Anglo-Iranian tensions. In 1987, all British staff were withdrawn following a series of diplomatic setbacks. They returned in January 1989 after Foreign Secretary Geoffrey Howe and Iranian Foreign Minister Ali Akbar Velayati agreed to resume contact. Then came November 29, 2011. Protesters stormed the compound, tore down the Union Jack, and raised the Iranian flag in its place. The attack followed joint American-British-Canadian sanctions, and Iran's Guardian Council had approved a bill expelling the British ambassador. London shut the embassy entirely and ordered Iran's London embassy closed. Sweden stepped in as Britain's protecting power in Iran; Oman served as Iran's in London.

Nearly five kilometers north of the main embassy sits Gholhak Garden, a 200,000-square-meter diplomatic compound in the Gholhak neighborhood. Tree-lined paths wind behind high walls where British diplomats and their families live. The compound also contains the Tehran War Cemetery, a reminder of the Allied presence during World War II. Iran has periodically demanded the return of Gholhak to Iranian ownership, and the site has been a target for government-orchestrated demonstrations. Since the former American embassy was taken over in 1979, Gholhak and the Ferdowsi Avenue compound have increasingly absorbed the anti-Western protests that once focused on the US mission.

The embassy reopened in August 2015, when Foreign Secretary Philip Hammond traveled to Tehran to raise the flag again. The diplomatic thaw followed Hassan Rouhani's 2013 election as president. Relations were upgraded in 2016 when charge d'affaires Nicholas Hopton was promoted to ambassador. But the pattern of rupture and repair continued. In January 2020, Ambassador Robert Macaire was arrested by Iranian authorities, an act Foreign Secretary Dominic Raab called a flagrant violation of international law. The compound on Ferdowsi Avenue endures as one of Britain's most volatile diplomatic postings -- a place where the distance between open doors and locked gates has never been more than a crisis away.