Yukiya Amano, the Director General of the U.N. nuclear agency, faces one of the world's most delicate diplomatic tasks following an historic deal reached between Tehran and six world powers this month.
His International Atomic Energy Agency (IAEA) is the international community's eyes and ears on Iran's nuclear programme. If Iran were to break its promises, Amano and his agency would be responsible for detecting and telling the world about the breach.
If Iran keeps its promises, it is also Amano who will report this and trigger sanctions relief for Iran.
He has no political mandate and never tires of stressing the IAEA's technical role. He must nonetheless manage and maintain a
fine balance between delivering data on Iran's nuclear activities and the huge political consequences this might have.
"If allegations emerge in the future about illicit nuclear activities, the IAEA will need to take a vigilant, but balanced approach," said Kelsey Davenport of the Arms Control Association. "The agency must investigate legitimate concerns but not overplay its hand."
Diplomats in Vienna said Amano was known for circumventing political traps.
"As director of a technical organization, he tries to avoid political quicksand. In the past, he has skilfully done this by strictly sticking to facts. I expect he will remain loyal to this strategy," said one diplomat.
Soft-spoken Amano has steered the IAEA through two of the biggest atomic issues since the world's worst nuclear disaster at Ukraine's Chernobyl plant in 1986: Japan's tsunami-crippled Fukushima nuclear power plant and the Iran file.
When he took office in 2009, replacing Nobel winner Mohamed ElBaradei, Amano pointed to the agency's work on medical and agricultural projects, saying that merely being the world's "nuclear watchdog" was not enough.
Much has been achieved in these fields, but the Iran nuclear deal has once more put the spotlight on the Vienna-based IAEA as exactly that.
Amano, a 68-year-old Japanese diplomat, has momentous tasks ahead of him, and other diplomats in Vienna say he has told them he is seeking a third four-year term to provide a safe pair of hands and a sense of continuity.
"He consistently acts in a controlled way," said the diplomat of Amano, who often repeats word for word the agency line when journalists bombard him with political questions at news conferences.
In 2011, the law-graduate published a document spelling out in detail concerns about possible military dimensions (PMD) of Iran's nuclear past, raising pressure on Iran to step up cooperation with the U.N. body.
This annex helped Western countries, which claim Iran had worked towards building a nuclear weapon, to tighten sanctions on Tehran, which says its atomic activities have been peaceful.
According to a new road map Amano announced alongside July 14's political deal, the next milestone will be Aug. 15, when Iran is due to provide a written explanation of outstanding issues to the IAEA and resolve any further questions by mid-October. Amano plans to submit a full report on PMD in December.
These are the only deadlines fixed in the context of the nuclear deal, and diplomats say October will be crucial as they wait for Amano to declare whether Iran has fully cooperated.
"There will be probably assertions as the report is being written about whether (Amano) will write a whitewash report so this can just be pushed through," said a second Vienna-based diplomat.
"But I think the answer is no. To remain personally and corporately credible he will need to write a report which factually represents what Iran has told them."
Some diplomats are sceptical that Iran will stop dragging its feet on PMD as it has done prior to the roadmap.
Amano, a keen sailor and skier, has stressed that while it's technically possible to wrap up PMD this year, the time frame depends on Iran. He said it was in Tehran's own interest to reach as quickly as possible closure of the PMD file.
"He has consistently tried to engage with Iran to make it address international concerns about its nuclear programme," said another diplomatic source with knowledge of the matter.
The so-called Additional Protocol which Iran agreed to implement under the deal will allow the agency to request access to any site in Iran to see if nuclear material has been diverted from peaceful purposes.
But this could become another headache for Amano as the document also allows for discussions of such requests to drag on.
Amano's importance as director of the body which reports on Iran's nuclear cooperation under this month's deal is only set to grow and the focus is on him to report on Iran's compliance with the agreement and allow for sanctions to be lifted.
"Much of (Amano's work) will impact Iran's political, procedural and technical normalization," the second diplomat said.SHOW MORE