A British-Iranian academic facing nine years in jail in Iran has told the BBC how he escaped on foot over mountains to start a new life in the UK.
Kameel Ahmady was convicted two months ago of collaborating with a hostile government. He denies the charge.
He decided to try to flee while on bail and appealing against the sentence.
Mr Ahmady trekked over a mountainous border to escape the Revolutionary Guards - a journey he described as "very long, very dark and very scary".
Mr Ahmady was born of Kurdish stock in western Iran. But his parents sent him to Britain when he was 18 for his education.
He remained there many years, studying at the University of Kent and the London School of Economics. Such was his affection for Britain that he applied for British citizenship before returning to Iran as an anthropologist.
His research focuses on child marriage and female genital mutilation (FGM) in Iran. This brought him to the attention of the authorities because he campaigned to raise the age at which girls can marry, which is currently set at 13 years old.
One morning in August 2019, a man came to his door in Tehran saying he was a postman. Mr Ahmady opened the door and 16 Revolutionary Guards stormed in. He was arrested and taken to the notorious Evin prison.
Mr Ahmady said he had been targeted not just because he was a dual national, but also because Iran wanted to retaliate after Britain seized an Iranian oil tanker off Gibraltar that was suspected of breaking EU sanctions.
"Being a dual national, you are always a potential case," he told the BBC.
"My chief interrogator said, 'You're very delicious,' a) because I was Kurdish; b) I was coming from a Sunni religious background as opposed with the majority of the Shia in Iran; and c) I was a researcher who was digging up sensitive issues. And I wasn't only a simple researcher, I was actually acting on my research and using it for awareness raising."
He spent three months at Evin prison where, he said, his interrogators played mind games with him.
"They treated me, on a human level, well. But don't underestimate the concept and the seriousness of so-called 'white torture' - the psychological pressure they put on you. And all these games are played stage by stage, and they're very well trained as to how to put a little bit of extra pressure on you when it's needed."
"There are all sorts of mind games, it's almost like a trade. You give me this, I'll give you that - a minute of a phone call needs all sorts of negotiation with your interrogators. Five minutes more extra fresh air than the half an hour that you're entitled to. And it is becoming really sad and petty because you want to be interrogated even more, not going back to the cell, which is almost like a grave."
After three months he was released ahead of the trial but monitored closely.
Last December, Mr Ahmady was convicted of collaborating with a hostile government, something he denies, after prosecutors claimed that a charity he had once done some work for had once received some funding from the United States. He also faced various other charges, including promoting homosexuality in his research.
He was sentenced to more than nine years in jail and given a fine of more than £500,000 ($683,000). But while out on bail, he decided to flee Iran.
He said: "The appeal was overturned. That was the moment that I decided to escape because I couldn't see myself staying in prison for 10 years and watching my son from a distance growing up. By the time I would have been released - if I was released - my son would have been 15."
So, without telling anyone but his immediate family, Mr Ahmady fled in secret, travelling over the mountains on foot to escape.
"I just simply left. I packed my bag with a shaving kit, a few books of mine, and a laptop."
"And warm clothes, because I knew I had to smuggle myself out of that train in the mountains. It was very cold, very long, very dark and very scary."
"I had to leave behind everything I loved, I worked for, all my human connections. It was so sad and scary. If I got arrested, I would have been back before the judge, and God knows what other scenarios that would be.
"It was a very hard and difficult decision. It was emotionally difficult. It was physically, mentally difficult. It was a move a made against my will. They pushed me out. And that was just so sad."
Last September Mr Ahmady was accused of sexual misconduct towards female colleagues. The allegations were anonymous, and emerged shortly before his court hearing. But the Iranian Sociological Association revoked his membership. Mr Ahmady denied both the allegations and the suggestion they played a role in his decision to leave.
Mr Ahmady said: "I find these allegations very upsetting. As I said at the time I take full responsibility for my actions and I find the sociological association's decision rushed and unfair. I do not accept any of these allegations. They are not related to the charges brought against me by the court which led me to escape, to restart my life in safety with my family."
Mr Ahmady now faces an uncertain future in Britain, without a job.
"I had to do what I needed to do. I couldn't stay and spend 10 years [in prison]. I can be much more useful outside and I have a responsibility towards my family."
The question now is how Tehran might respond and what impact may be felt by other British-Iranian dual nationals.