‘The embassy is being invaded. The ambassador has had to lock himself in his office upstairs, and there are people on our balcony. Your government is responsible for the safety of our diplomats and embassy. We will hold you accountable…’ The voice at the other end of the line was calm, though there was no mistaking the underlying aggression. ‘The Vienna Convention is very clear about the responsibility of host countries for diplomatic missions.’

I received that call in the autumn of 2017, when I was coming to the end of my second year as Britain’s ambassador to Iran. A large group of demonstrators had been campaigning loudly outside the Iranian embassy in London for the release of Nazanin Zaghari-Ratcliffe, who had been illegally detained since April 2016 in Evin Prison in northern Tehran. The protestors had breached the embassy gates, and a few had managed to get onto the balcony outside the ambassador’s office – the same balcony that black-clad, balaclavaed SAS soldiers abseiled onto when they recaptured the embassy from Khuzestan terrorists in May 1980. Perhaps it was little wonder that the Iranians inside, 37 years later, were fearful.

Araghchi will seek to keep Iran on the right side of Russia and China

To everyone’s relief there was no rupture in diplomatic relations that autumn night. Eventually I was able to reassure the Iranians that their diplomats and embassy were not at real risk, and the protestors limited themselves to unfurling a banner on the balcony before being escorted away. The Iranian diplomat who had called me was Sayed Abbas Araghchi. He was then a deputy........

© The Spectator