Iran nuclear talks: How negotiators broke the ice
As Western diplomats hail positive progress at talks with Iran on its nuclear programme, the BBC's James Reynolds in Geneva looks at what may have brought the two sides closer together.
For years, negotiators from the six world powers and Iran struggled to find ways to understand one another. The only thing they appeared to share was the same awkward posture around their cavernous negotiating tables.
But diplomats in Geneva found an unusual source of common ground with their new Iranian counterparts: concern for the status of the Iranian foreign minister's back.
In recent days, Mohammad Javad Zarif posted Facebook updates on his debilitating back pain - he was even pictured on Twitter lying down on his flight to Geneva to protect his back.
As soon as the formal talks began on Tuesday, diplomats took turns to ask after Mr Zarif's health and offer him advice.
"I did. We all did," said a senior US administration official with a smile.
Once this common ground was established, officials got to work. Mr Zarif used a PowerPoint presentation on his black Lenovo laptop to outline a plan to end the conflict over Iran's nuclear ambitions.
For the first time in many years, diplomats say that they engaged in detailed discussions about the nature of Iran's nuclear programme. The talks were conducted in English - a change from previous rounds, where consecutive translation between English and Farsi slowed the pace of dialogue.
"I've been doing this for two years and I have never had such intense, detailed, straightforward, candid conversations with the Iranian delegation before," said the US official.
Neither side will talk about what is in Iran's plan. One diplomat at the talks suggested that this was a positive sign - real discussions do not take place in public.
But any final agreement will have to address the demands that the world powers have made in recent years: stop the enrichment of uranium; export existing stockpiles of low- and medium-enriched uranium; suspend work at the heavily fortified Fordow enrichment facility.
In return, Iran's demands of the outside world (and the West in particular) are well-known: lift sanctions and recognise what the Islamic Republic calls its right to enrich uranium.
Those competing demands will no doubt be discussed when teams of nuclear and sanctions experts hold their own talks in the next few weeks.
This round of negotiations also highlighted an important point: Iran and the United States have quietly settled into the habit of holding direct, openly acknowledged talks.
Late on Tuesday, the Iranian and US delegations met on the sidelines of the conference for an hour. The US described those talks as "useful".
This meeting followed two historic encounters in September: the face-to-face meeting between Mohammad Javad Zarif and US Secretary of State John Kerry, and the 15-minute phone conversation between Presidents Obama and Rouhani.
The taboo preventing either side from holding (or acknowledging) direct talks with the other has disappeared.
"It is no longer the Rubicon that it was - and that is a good thing," said a US official in Geneva.
There is much also for Iran's new government to take away from this round of talks. President Hassan Rouhani was elected in June on a promise to end needless confrontation with the outside world. His government will want to show that this Geneva conference marked an important step towards ending the Islamic Republic's isolation.
"To be fair to our friends in the P5+1 [the world powers group], they showed a new approach," said Mohammad Javad Zarif at his closing news conference.
The two days of talks in Geneva appeared to run down his final reserves of strength. Mr Zarif was escorted from the news conference in a wheelchair. But he did manage a wave.
After years of mistrust, it took a bad back to break the ice.