Tae Yong-ho says he was 14 years old when he first began to comprehend the true cruelty of the songbun, Kim Il Sung’s class system.

It was August 1976, and the Great Leader was expelling people whose loyalty might not be guaranteed. Tae’s parents, members of the “core class”, were safe. His aunt, uncle and two cousins, members of the “wavering class” because of suspected links to Japanese collaborators, were ordered out of Pyongyang. Tae watched as his mother and aunt wept. “We were just one family at the time, every night we ate together,” he says. “I asked my mother, why?”

At 58, with his black hair thinning, Tae has already lived a remarkable life. He progressed from rare foreign language training in North Korea to become a diplomatic envoy for three generations of Kim dynasty rulers. Then, in 2016, while serving as deputy ambassador to the UK in London, he and his immediate family defected, making him one of the most prominent North Koreans to break with the totalitarian regime. He is now an opposition lawmaker in the South Korean parliament and outspoken critic of the 37-year-old dictator, Kim Jong Un.

We’re scheduled to dine at Akira Back, a contemporary Japanese restaurant named after its chef patron, on the 12th floor of the opulent Four Seasons Hotel, just off the stately boulevard leading up to royal and presidential grounds in the heart of Seoul.

As I wait at a downstairs booth, two young men appear at the upstairs landing, near the restaurant’s bustling open kitchen. Their eyes scan the lofty, wood-panelled room. Tall and well-built with carefully styled mops of black hair and ear pieces, they look as if they’ve just stepped offstage at a K-pop concert. They are in fact bodyguards and Tae, at permanent risk of assassination by his former countrymen, never goes anywhere without them.

Isolated, nuclear-armed and with a population subjected to threats of torture, brainwashing and hunger, North Korea poses one of thorniest problems facing the international community. In the eyes of many of the journalists, academics, diplomats, security analysts and spooks who compose the niche world of North Korea watchers, Tae is an undisputed authority on the secretive Kim regime. Tens of thousands of North Koreans have fled the country over the years — each with a story well worth listening to — but few have the same depths of insight into the inner machinations of this long-running dynastic dictatorship. Nor has anyone better understood and spoken so publicly about the culture of the elites who’ve kept the regime from collapsing into chaos across seven unlikely decades.

Tae’s initial concerns are far more prosaic than snipers sent from Pyongyang. He is watching his weight after his health club visits fell victim to the coronavirus pandemic. He would like, he says, something “as small as possible”. My sympathy for my guest’s weight-loss ambitions is outmatched by fears of a truncated conversation. A touch wickedly, I steer us toward the set lunch menu, suggesting there will be a few small dishes that we don’t need to finish. Tae acquiesces to the food but politely turns down the suggestion of a bottle of soju; he has political campaign meetings to attend this afternoon.

Tae sinks into the plush bench cushion, and reminds me that this is not his first lunch with the FT. As deputy ambassador to the UK, on several occasions he ventured from the Democratic People’s Republic of Korea’s embassy in an unremarkable west London suburb for lunches overlooking the Thames with visiting Seoul correspondents and their editors.

Tae speaks with remarkable fluency, his precise enunciation carrying echoes of an older generation of officials from Hong Kong or Singapore. Our first course — a modest garden salad lifted by an exceptional goma yuzu dressing — has arrived. He expertly twirls the green leaves with his chopsticks and explains the circumstances that resulted in a mastery of a foreign language and a life abroad, amazing fortune for someone born into one of the world’s poorest and most cut-off countries.

His family’s first stroke of luck, he says, was his paternal grandfather siding with the Workers’ Party during the brutal Korean war of the early 1950s. Tae’s father was born in North Hamgyong province, just across the frozen border from China’s north-east, but as a member of the core class, coupled with brilliant academic abilities, he was able to live in Pyongyang first to study, and later to teach architecture. Tae smiles as he recalls his childhood encounters with Russian diplomats and their wives walking the streets of Pyongyang in the 1960s: “I watched those big noses, blue eyes, these Russians, every day. To me, foreigners weren’t so strange.”

At 12, following a series of exams, he was accepted into the state’s foreign language institute. Tae credits his mother for resisting the preferences of the day for elite parents to direct their princelings into mathematics or physics. “My mother said ‘no, you should be an English interpreter . . . look at the Russian embassy, if you speak foreign languages you can go out and work in those kinds of embassies worldwide’,” he says. “That actually changed the whole course of the rest of my life.”

Learning English eventually meant exposure to foreign media — and hints that life abroad was different from what the students had been led to believe. Pyongyang’s propagandists at the time pumped out endless anti-American diatribes, depicting the US as full of misery and suffering, its leaders as murderous brutes. Tae and his classmates, however, consumed American movies and British instructional courses. Their teachers, who had never travelled abroad, lacked confidence in their own pronunciation and were forced to use the kinds of foreign-produced media that even top officials were banned from accessing.

Pictures of a full English breakfast left Tae mystified. “How could it be possible for just breakfast you have eggs, bacon, milk, butter, cheese, all of these things? We thought it was propaganda.” And after watching Mary Poppins and The Sound of Music he wondered how it was that a country like America, which killed people at random, could also produce such good films. “I started to have other thoughts.”

The waiting staff take a break from fastidiously topping up our glasses from bottles of San Pellegrino to deliver white ceramic plates. Tae leans forward to inspect the sashimi — a collection of halibut, octopus, salmon, shrimp, salmon roe and tuna akami, glossed with a translucent tosazu sauce. After considering the restaurant’s glassed ceiling high above us, he playfully suggests why Japanese restaurants traditionally had low ceilings: to stop samurais from drawing their swords during meals.

Tae’s development of secret misgivings as a teenager in the 1970s remains instructive today. South Korea in December introduced new laws threatening jail time for human rights advocates who send information from the outside world — including movies, television dramas and music as well as more pointed political material — into North Korea. Moon Jae-in, the president and former human rights lawyer pursuing rapprochement with Kim Jong Un, hopes the move will help draw Kim back to the table for nuclear talks.

But Tae is fiercely opposed, arguing that one of the only realistic ways to promote long-term change in North Korea is to give the country’s 25m people as much exposure to outside information as possible. He notes that Kim Jong Un has in recent months introduced new laws stipulating that people caught distributing such material can be executed — an admission of the existential threat the North Korean leadership sees in enlightened masses.

Indeed, despite earlier hopes that the Swiss-educated dictator might have embarked on a slow march of economic reform along the lines of the cadres in China or Vietnam, potentially opening North Korea to more outside investment and interaction, Tae believes the reverse is now happening with the creation of “new systems and structures” for control and surveillance. “The Kim family feels great unease,” he says.

After an interlude of bite-sized croquettes — botan ebi shrimp, sea urchin and caviar all wonderfully overpowered by truffle — our main sushi course arrives. Happily, Tae seems to have forgotten his designs on a light lunch. After mixing wasabi into soy sauce we pause the conversation for a few minutes to attack the sushi in single bites. The almost-rich anago, saltwater eel, contrasts beautifully with the negitoro, a tower of small chunks of fresh tuna wrapped in slightly crisped seaweed.

Ban Ki-moon, the former UN secretary-general and a critic of the new South Korean laws, briefly stops by our table for a pleasant commotion of bows and two-handed business card swaps. The sight of one of the country’s elder statesmen draws hushed whispers from nearby booths and tables of perfectly groomed twenty- and thirtysomethings.

Returning our chopsticks to their small stone holders, we pick up Tae’s life as a diplomat in Europe in the 1990s. With the lifelines of Soviet-era state support severed, the facade of the Kims’ socialist paradise swiftly crumbled and the country plunged into famine. North Koreans were told they were on an “Arduous March”. International estimates of total deaths stemming from starvation range from the hundreds of thousands to several million.

Chief among Tae’s responsibilities during this period, while posted to Denmark and Sweden, was to perform an embarrassing dance traipsing cap-in-hand to diplomatic counterparts, while simultaneously rejecting all notions that the regime itself was to blame. Meanwhile, Kim Jong Il was spending hundreds of millions of dollars refurbishing the Kumsusan Palace of the Sun, the residence-turned-mausoleum of his late father. The Dear Leader was also busy developing nuclear weapons. “To get the food aid, I had to defend [the regime] again and again and again,” Tae says, banging the table with one hand. Despite keeping his guard up in the face of his western counterparts, in his own mind, Tae says, he was becoming “very sad”.

Tae was still part of the regime. And Pyongyang’s network of foreign emissaries are notorious for their trafficking of contraband in order to make money for the Kims, and for their involvement in obtaining, by hook or by crook, any secrets that can assist the development of nuclear weapons. Asked about his involvement in these illicit activities, Tae says such roles were delegated to other embassy staff. Although he does offer a hint of empathy for his former colleagues. The North Korean ideology of juche, self-reliance, extended to those diplomats tasked with generating revenue, he says. That meant they were often left to pay their own way abroad.

On the other hand, North Korean diplomats are not allowed to do anything alone, creating a culture of fear as they are forced to spy on each other. If they are deemed to have wronged the regime, their status doesn’t offer protection from barbarous consequences. “Everyone knows, if you said something against the system or leader, you would be disappeared and sent to [one of the] prison camps. From time to time some of your colleagues just disappear without explanation.”

Dessert and coffee arrive; chilled plates with a moreish yuzu cheesecake and scoops of refreshing mango sorbet sit next to a trail of dark crumbed biscuit. Steaming Americanos for both of us.

Despite a series of unverified rumours, the details of exactly how the day of Tae’s defection unfolded remain murky. He has not spoken publicly about it. On the final decision to risk everything and leave his post in London, Tae says he was spurred by an immovable realisation that the young dictator was not going to take the country in a new direction. The idea of leading his own sons back to life in Pyongyang after they had spent so much time in the west became unconscionable.

“If [Kim] dies naturally then we must wait another 30 or 40 years. I have to answer to my [future] grandchildren,” Tae thought at the time. “So I decided to defect in order to give freedom to my sons.”

Over the years other high-level defectors have taken on new secret identities, seeking to live out their days in anonymity. Ko Yong Suk, the North Korean leader’s aunt who was tracked down by former FT and Washington Post journalist Anna Fifield in 2016, had lived in obscurity in the US since 1998, running a dry-cleaners with her husband. Tae feels safe with his security detail, but notes North Korea’s record of assassinations on foreign soil, including Kim Jong Nam, the current leader’s half-brother, who was killed by nerve agent in a Malaysian airport four years ago.

But now that Tae is in Seoul he wants to keep using his newfound freedom of speech to send a message back to Pyongyang — an endeavour made easier by the platform given to him in the National Assembly seat he won easily in April. “My real mission as a politician is that I want to tell the North Korean elite that there could be an alternative for their future,” he says.

Following the polite intervention of Tae’s patient parliamentary aide, we wipe our hands and ready our masks.

Tae has a parting message for the new Biden administration: do not strike an Iran-style nuclear deal because it would essentially legitimise Kim Jong Un and justify his policies. Instead, he wants the US to keep enforcing tough sanctions. Ultimately, Tae doesn’t discount Kim’s strength. But with enough pressure he believes the dictator’s downfall is a possibility — a prospect that might come about much more swiftly were China ever to enforce sanctions properly.

“A very small spark” is all that it would take, “like what happened at the Arab Spring.” As we step out into the snowy streets of democratic South Korea, I wonder whether anyone in communist North Korea, barely 50km away, is listening.

Edward White is the FT's Seoul correspondent, covering South Korea, North Korea and China

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