For the actual swearing-in ceremony of so-called President Ahmadinejad in Iran, HM Ambassador Simon Gass brusquely elbowed his deputy Patrick Davies out of the way and attended to represent The Queen.

To the displeasure of The Times:

The Foreign and Commonwealth Office said that it had dispatched the ambassador because the international community had to keep talking to the Iranian regime about its nuclear programme, so “communication channels have to be kept open”. It had indicated its displeasure at the events of the past two months by witholding the customary letter of congratulation. It calls this “hard-headed diplomacy”.

Somewhere between London and Tehran, this rather nuanced message apparently got lost in translation. Mr Ahmadinejad did not welcome the Western envoys to yesterday’s ceremony: he mocked Britain, the US and other countries that had withheld congratulations for thinking that he cared about their approval.

Fair enough.

Except that had the Ambassador not attended this gruesome ceremony the regime might simply have frozen him out personally from any senior contacts for the rest of his posting. Whatever chances there might have been for him to influence anything in the years to come could be lost.

Or maybe not. Perhaps the Iranian regime would be more likely to respect and deal with an Ambassador and a government which appears to stand up for something specific, even defying the regime itself.

The best approach has to be agreed by balancing Principle against What Might Work Best. In this case there is no obviously good answer, the more so when the United States has no stomach for a confrontation and is hoping for the best by going along with the nasty facts on the ground.

Basically, when diplomats are in a dirty place they get dirty.

That’s part of the charm of the job.