We are not yet approaching the level of the events of November 1979 when Iranian students overran the US Embassy and held 52 Americans hostage for 444 days. But the seizing of high-level local staff at the British Embassy gives this crisis its own flavour: in the 1979 Islamic Revolution the Iranians who worked at the US Embassy were left alone.

Today the defunct US Embassy in Tehran houses a detachment of Revolutionary Guards and an anti-American museum. It is the scene of ritual and desultory anti-US protests on every November 4, the anniversary of its seizure. The sprawling compound was stormed after the US agreed to admit the Shah for medical treatment for cancer. Tehran, which suspected that the US was conspiring to restore him to power, saw this as a hostile act.

The seizure was a devastating blow for moderates in the provisional revolutionary government. Ayatollah Khomeini, father of the Islamic Revolution, endorsed the takeover more for reasons of domestic than foreign policy: it cemented the revolution for him and his radical supporters who did not share the moderates’ hopes of a liberal democracy and accommodation with the West.