The British Embassy on Ferdowsi Avenue in Tehran is — usually — an oasis of tranquillity in the midst of a teeming, polluted city. Behind its high walls and formidable security gates are beautiful landscaped gardens with fountains, a lily pond and towering trees, a splendid ambassador’s residence and other pleasant buildings where the British diplomats, supported by about 100 Iranian staff, work each day. A clock tower dating from 1870, its mechanism built by E. Dent & Sons, who made Big Ben's clock, flanks the residence.

It was in these grounds that Churchill recovered from his gruelling work 65 years ago at the Tehran conference, which brought together for the first time the leaders of the three main Allied powers fighting Nazi Germany. The main talks were held across the road at the Soviet Embassy, on whose steps the famous photograph of the trio was taken, but they also came together at the residence on November 30 when Churchill celebrated his birthday.

In the Shah’s days, the embassy hosted oilmen and arms dealers. Its importance declined after his overthrow and it was shut three times in the following decade.

Whenever Iran’s relations with the West are strained, the embassy of the “Little Satan” almost invariably becomes the target of protests. The Iranian Government also changed the name of an adjacent thoroughfare from Churchill to Bobby Sands Street in honour of the IRA hunger striker (the sign reads “Babi Sandz”).

Diplomatic relations between Iran and Britain were downgraded after Iran issued a fatwa against the British author Salman Rushdie in 1989, but in the late 1990s Britain renovated the historic embassy. The reformist Mohammad Khatami had just been elected President and Whitehall was eager to rebuild relations with the oil-rich country.

Those hopes now look forlorn. In December a mob invaded the embassy’s other compound in north Tehran. Last week a crowd demonstrated at the main compound. Security has been stepped up, the diplomats’ families have all been evacuated — and the regime is painting the embassy as the nerve centre of a Western conspiracy to destroy the Islamic Republic.

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