Arash Hejazi smokes hand-rolled cigarettes, which he keeps in a silver case. He speaks a considered, professorial English, idiosyncratic only because of his Iranian accent. Despite having endured much since the summer of 2009, he exudes the guileless energy of a very young man (he is 37).
You may not have heard Hejazi's name before, but it's likely that you already know something of his story. During the Green Movement protests that swept across Iran in the summer of 2009, Hejazi was standing next to a young woman when she was shot. He bent over her prostrate body as she lay dying, in an unsuccessful attempt to save her life. A video of those events was posted online and soon became international news: images of Hejazi and the tragic girl were transmitted into hundreds of millions of living rooms. That girl was Neda Agha-Soltan, and she became a symbol of a new Iranian generation, their dream of freedom, and the brutal suppression of that dream.
Two-and-a-half years on, Hejazi is still haunted by the moments in which Neda lost her life:
"Before she passed away she looked into my eyes. I never understood what she meant by that look; it could have just been fear, or the empty look of someone who is dying. But at that moment I had the feeling that she was trying to tell me something. It was the look of someone who has been hunted down and is dying: what would a person be trying to say in those last moments?"
Hejazi's involvement in Neda's story changed his life forever. He left Tehran and has been unable to return. He now lives in England, and today we meet in London to talk about the memoir he wrote in the wake of these experiences, The Gaze of the Gazelle. But before all this, he was a successful fiction writer and publisher in Tehran - he founded the publishing company Caravan Books - as well as a qualified doctor. Hejazi was in England to attend a publishing course at the time of the 2009 Iranian presidential elections: he voted for Mousavi at the Iranian embassy in Kensington before returning to Iran the next day.
"The atmosphere in Tehran was terrible," he says. "The news had come through that Ahmadinejad was declared the winner. Everyone I spoke to believed the election had been rigged. People were out on the streets."
The popular uprising that followed - and the brutal response of the Islamic Republic - reverberated around the world. On June 15 millions took to the streets in Tehran in one of the largest demonstrations in history. Five days later, Neda was shot as she participated in a street protest close to the offices of Hejazi's publishing house.
"On that day I was one of the cautious people who didn't want to go out because of the danger. But in my office a few people wanted to go. One young man was insistent he would go out, so I said: OK, if you have to go, I will come with you.
"There was a crowd of around 500 outside my office, being attacked by Basijis on motorcycles. We ran back through an alleyway with some others, and at the end of that alleyway Neda was shot.
"At that point, you switch off your emotions. I lay her on the ground and tried to stop the bleeding. But there was no way to save her: the bullet had hit her aorta and her lung.
"When I realised she was dead I stood up. Now I was overwhelmed by fear: there could be more bullets at any moment. My friend was in a state of shock. We took him back to the office and gave him a drink of water. I took his mobile phone and saw what he had recorded, and said: I'm going to post this online."
Hejazi must have known that this decision would bring the ire of the Islamic Republic down on him: so why did he do it?