It was an unlikely friendship - the prison guard and the prisoner.

They had met just two months earlier - in May 2019. Jeon was one of several guards at Onsong Detention Centre in the far north of North Korea. He and his colleagues kept Kim and a few dozen other inmates under surveillance 24 hours a day whilst they awaited trial.

Kim caught his eye with her refined clothing and demeanour.

He knew she was there because of her role in helping their fellow countrymen who had already fled a life of desperation.

Kim was what was known as a broker. She helped keep channels open between those who had fled and families left behind. This could mean facilitating money transfers or phone calls from the defectors.

And it was lucrative work for the average North Korean.

Kim was paid about 30% of the cash as commission, and an average money transfer is about 2.8m won [£1,798], research suggests.

On the face of it, Kim and Jeon couldn’t have been more different.

While she made her money illicitly, learning as she did about the world outside North Korea’s strict communist regime, Jeon had spent the past 10 years in the military as a conscripted soldier. He was steeped in the communist ideology of the country's dictatorship.

What they didn’t realise was how much they had in common. Both were deeply frustrated by their lives and felt they had now run out of road.

For Kim, the turning point was her jail sentence. This wasn’t her first prison term, and she knew that as a second-time offender she would be more harshly treated this time around. If she did make it out of prison alive, then returning to a life of brokering - and potential arrest again - would have been an extremely risky thing to do.

Kim’s first arrest was for a particularly dangerous type of brokering - helping North Koreans escape over the border into China - the very route that she and Jeon would go on to take themselves.

“You can never do this line of work without connections in the military,” she says.

She would bribe them to look the other way, and was successful for six years, earning good money in the process - US$1,433-2,149 for each person she helped leave. That meant getting just one person across was the equivalent of a year’s income for the average North Korean.

But eventually the very contacts in the military who had paved the way were the ones who betrayed her.

She was sentenced to five years in prison. When she left she had intended to give up brokering. It was just too risky.

And then she made a discovery that would force her to think again.

“I told them I would pay as much as they would want me to and I begged and begged” Kim

Her husband had remarried while she was in jail, taking their two daughters with him. She needed to find a new way to survive.

She decided that even if she did not dare help people escape any more, she could still use her contacts to do a different - slightly less risky - type of brokering. She would facilitate transfers of money from defectors in South Korea, and host illegal phone calls from them.

North Korean mobiles are blocked from making or receiving international calls, so Kim would charge a fee for receiving calls on her smuggled Chinese phone.

But she was eventually caught out again. As she took a boy from her village into the mountains to take a call from his mother, who had defected to South Korea, they were followed by the secret police.

“I told them I would pay as much as they would want me to and I begged and begged. But [the official] said because the son already knew everything they could not hide my crime and cover for me.”

In North Korea, activities which involve or suggest a relationship with an “enemy state” - South Korea, Japan or the US - can earn a North Korean a stiffer sentence than killing someone does.

Kim realised that life as she knew it was over. When she first met Jeon she was still awaiting trial, but she knew that as a second-time offender she had a tough time ahead of her.

Jeon, although not fearing for his life, was also feeling deeply frustrated.

He had begun his mandatory military service - routine tasks such as guarding a statue of North Korea’s founder and growing grass for livestock - intending to eventually become a police officer, a childhood dream.

But his father had now broken the truth to him about his future.

“My father sat me down one day and told me that realistically speaking a person of my background would never be able to make it [into that position],” he says.

Jeon’s parents, like their parents before them, are farmers.

“You need money to advance in North Korea… It’s getting worse and worse... Even the test you take to graduate from university, it’s now taken for granted that you bribe professors for good results,” says Jeon.

Farming families have been hit by a poor harvest recently

And even for those who do make it to a top college, or graduate with the highest honours, a bright future is not guaranteed unless that person has money.

“I know someone who graduated from the [prestigious] Kim Il-sung University as a top graduate, and yet has ended up selling fake meat in the market,” he says.

For much of the population, simply surviving is a struggle.

Living conditions may be better than they were in the early years of Jeon’s life, when the country was ravaged by a deadly four-year famine dubbed “The Arduous March”, but they are still extremely tough.

So having been told his ambition to become a policeman was impossible, Jeon had started thinking of another way to change his life.

It was still just the seeds of an idea when he met Kim, but as they talked, the idea took hold.