Yet the interim deal does precisely that.Western concessions will enable Iran to replenish its foreign currency reserves. They will relieve three sectors — petrochemicals, cars and aviation — that are largely controlled by the Revolutionary Guards and the Supreme Leader's business empire. They will provide the regime with a cash bonanza and help its rulers stabilise the economy — in the first 24 hours after the agreement, the rial appreciated by 5 per cent against the US dollar, and European and Asian carmakers that had quit Iran because of sanctions are lining up again for deals.

Thus the regime constituents least likely to support accommodation with the West and most invested in Iran's nuclear weapons quest will benefit from these measures long before the nuclear threat is neutralised. Given the dual-use nature of car industry and petrochemical technology, Iran will not only benefit financially but regain access to critical components of the nuclear programme it is currently finding hard to procure.

Even worse, the agreement will reopen banking channels for the regime to exploit. While the language of the agreement appears foolproof — allowing only non-sanctioned entities to benefit from such channels-it is easy to imagine how Iran will take advantage of such relaxation for its own proliferating activities, considering how it cheated the financial system in the past. This is the worst possible disincentive for Iran at a time when its military nuclear programme is dangerously close to completion. 

Thanks to the sanctions regime, Western diplomacy was winning the race against a nuclear Iran. There is now a reasonable chance that Iran will be the victor instead.