The way the Iranians tell it, it's a done deal. In the light of the International Atomic Energy Agency closing its file on the "Possible Military Dimensions" of Iran's nuclear programme, sanctions are about to be lifted. If so, Iran will become even more politically and economically powerful in the Middle East.
President Hassan Rouhani said this was a "great moral, political, and legal victory" which means sanctions "will be lifted in the month of Dey (December 22-January 20)", and that the IAEA had "admitted that Iran has never deviated from its peaceful path…" It's the way he tells them, but it's not necessarily the way it is. The closing of the file is part of the process leading to the end of sanctions, but the report left reasons to remain suspicious of Iran's intentions and the way ahead.
The report makes clear there was a military aspect to Iran's programme prior to 2003, involving the computer modelling of a nuclear explosive and the development of detonators. It also found that Iran continues to be far from transparent about its current activities, and may be dragging its heels in removing facilities related to testing nuclear weapons equipment. No centrifuges have been dismantled and some equipment seems to be merely being moved from one site to another. Nevertheless, the file is closed.
However, to reach "Implementation Day" - the lifting of sanctions - Iran must now complete a range of tasks. The government says it will do this in three weeks, which seems ambitious. Among the tasks are to reduce its enriched uranium stockpile to 300kg, dismantle its centrifuges so that only 6,000 remain active, and pour concrete into the nuclear reactor at Arak so it cannot be used to make plutonium. If this is not done within three weeks, it is doubtful the US and others will agree to lift sanctions, at which point tempers may begin to flare.
Iran's Foreign Minister Mohammad Zarif has already said that the US should lift sanctions before Iran meets its obligations. The IAEA has hinted at this saying "Iran needs to complete the 'necessary preparatory steps' before Implementation Day". However, there is nothing in the original agreements about "preparatory steps". It is unlikely that the USA, France, and the UK would be satisfied with this, especially in the light of Iran firing a nuclear-capable ballistic missile in October, which they claimed violated the agreement.
The Foreign Office regards the Iran nuclear agreement as the signature British diplomatic achievement of 2015. However, if Iran continues to prevaricate and obfuscate they will be reminded of the saying Ronald Reagan used to quote to Mikhail Gorbachev: "Doveryai, no proveryai" - "trust, but verify". This summer's deal was short on detail about how to do either. It is about to be tested.
Tim Marshall is former diplomatic editor at Sky News and now runs the website thewhatandthewhy.com