The most striking observation of diplomats negotiating with the Iranians was the gulf between the belligerent rhetoric pouring out of Tehran in recent days and the intense but more nuanced conversations inside the Geneva villa.

It was unclear before talks began whether Iranian negotiators would even discuss their nuclear programme, given their public posturing about non-negotiable rights. In the end they did, and listened intently to the clarifications they had sought about what exactly was on offer.

Those involved said that last week’s public unveiling of the underground plant at Qom was the game-changer — not just for Iran, but also for Russia, which made it clear that it was unimpressed by being lied to.

Russia was said to be instrumental in bringing Iran’s attention back to the nuclear issue when it attempted to veer off into its well-trodden narratives about historic injustices. Moscow seems to have shifted the burden of avoiding sanctions from Western shoulders to Iranian ones.

The concessions have not been all one way. By seeking a second round of talks, including discussion of Iran’s regional agenda, and finding a tolerable, even advantageous, solution to Tehran’s demand for high-enriched uranium, the international community has allowed Iran to save face.

Tehran, however, has much to prove. While foreign reprocessing of its low-enriched uranium stockpiles would slow any sprint towards a nuclear bomb, the centrifuges keep spinning.

And without a tougher inspections regime, Tehran’s claims that the Qom plant was its only hidden site are hard to prove. Both sides have bought valuable time but it is still up to Tehran to explain away well-founded and lingering military suspicions. The heat is off Iran for now — but it will not stay that way for ever.

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