Imagine playing a game of Pictionary with a group of Oxford University students who are unable to recognise the Taj Mahal, the Pyramids or the Eiffel Tower.

Welcome to the parallel universe of North Korea, where some of the hermit kingdom's brightest young minds have a lack of worldly knowledge which would shame a Western primary school student.

In 2011 writer and journalist Suki Kim went undercover for two terms teaching English at the Pyongyang University of Science and Technology, just outside the capital of the world's most secretive country.

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Suki Kim (left), arrived for her first term in North Korea in July 2011 and left at the end of her second shortly after the country's Dear Leader, Kim Jong-Il (right), died in December of that year

Students at the Pyongyang University of Science and Technology doing their mandatory morning exercises

Miss Kim taking a class. One student once asked her if it was true everyone in the world spoke Korean. Portraits of Kim Il-Sung and Kim Jong-Il hang on the wall above the blackboard

Posing as one of the Christian missionaries running the facility, Miss Kim spent months secretly documenting her experiences for a book, 'Without You, There Is No Us: My secret life teaching the sons of North Korea's elite'.

The 270 boys aged 19-20 were the offspring of some of the regime's most loyal citizens - some of the few allowed to live in the capital outside of which the vast majority are stuck in grinding poverty in the countryside.

Their new teacher was getting up at 5am every day to write-up notes she had taken on her experiences, making sure she copied everything to five USB sticks and left nothing on her laptop which could be spied on by her hosts.

If Miss Kim, then aged 40, had been caught, she risked being branded a spy and being thrown in one of North Korea's gulags, or forced labour camps, where 120,000 political prisoners are thought to be held.

Every piece of material for every lesson had to be submitted and approved for use by a shadowy group known as the 'counterparts' - North Korean staff overseeing the lessons of the foreign teachers who had been brought in.

Students on a cold and snowy day after an exam, with the Kimilsungism Study Hall in the background

Miss Kim wrote her book (left) after months of secret note-taking. The Juche Tower in Pyongyang (right)

An enclosed walkway that connects all buildings at the PUST campus, including the classroom building on the left. A Pyongyang smokestack belches fumes in the distance

By Miss Kim's second week the counterparts had approved various games, including trivia contents, spelling competitions and Pictionary.

And yet, for North Korea's best and brightest, 'photos of the United Nations, the Taj Mahal and the Great Pyramids of Giza elicited only blank expressions'.

They knew about Bill Gates from their previous universities, but had no idea how Mark Zuckerberg and the website he created, Facebook, had revolutionised the way the rest of the world communicated.

Miss Kim wrote: 'A few guessed the names of the Eiffel Tower and Stonehenge, but only after much hemming and hawing.

'Hardly anyone knew what country had first landed men on the moon, despite the fact that they were science and technology majors.

'Asked what year computers had been invented, most had no idea; it was only after much consultation that one team ventured a guess: 1870.'

Miss Kim told MailOnline: 'In a way, why would they know? They have never been taught about the outside world.

Three uniformed students on guard duty outside the IT building. The sign reads: 'The Sun of the 21st Century, General Kim Jong-Il'

Students on sports day with the Forever Tower to the right, on which is inscribed 'Our Great Leaser is Always With Us'

Students often watched from their dormitory windows while Miss Kim practiced playing basketball below

'They didn't even know about the existence of the internet. There is only one TV channel about the Great Leader and one newspaper about the Great Leader [North Koreans' term for Kim Il-Sung, the country's founder and first leader, who is considered to be immortal and the country's 'Eternal President'].

'But on another level they were the elite. If any of them did know more the fear and the consequences of being exposed were so great they never let it be known.'

One student asked Miss Kim if it were true that everyone in the world spoke Korean, as it was 'so superior that they spoke it in England, China and America.'

Many of the boy's families lived as little as 10 minutes drive away in Pyongyang, but they were hardly ever allowed to see them or have any contact at all during term time.

One student's father stopped by the campus to see him but was turned away and all he could do was leave a note.

Another was late for lunch one day because his mother had come to the gate with rice cakes and roast chicken as it was his birthday.

Miss Kim wrote: 'He was an only child, and she wept during their twenty-minute meeting, so he told her, "If you keep crying, I am going to go back inside."

'He was laughing as he said this before his friends, but his eyes watered.'

Miss Kim in the classroom with the lyrics of a North Korean song which she translated with her students

Eating instant ramen outside the Seventh Pyongyang Autumn International Trade Fair on a rare outing

All the students wore lapel pins featuring the face of Kim Il-Sung.

Even during the bitterly cold winter months, groups of six students at a time dressed in martial uniforms were expected to stand guard all night outside the campus's hulking grey Kimilsungism Study Hall.

It is where they went to study Juche, Kim Il-Sung's pseudo philosophy of self reliance, and many performed such duties outside similar halls in the areas they grew up in since they were teenagers.

Miss Kim is unnerved by the extent to which her students lied, be it about the myriad achievements of Kim Jong-Il, the country's 'Dear Leader' at the time, or what they had been up to that morning.

She said: 'It's a whole world of lies. Coming from a world where everything is a lie in some ways it's just been ingrained but they also lie because they are constantly being watched.

'The system has an absolute hold. They lie to protect the system from the outside and also out of fear.

'They were lovely at the same time and also very sincere but their system is a system built on lies.'

A highlight of Miss Kim's time at PUST was when she fought successfully so that one of her classes could watch Harry Potter and the Prisoner of Azkaban.

Students taking part in their final exam. One class was ecstatic at being allowed to watch Harry Potter

The sign on this building in the capital reads 'We are happy'. Downtown Pyongyang was only around 10 minutes drive from PUST, but students were never allowed out to visit their families during term time

She said: 'They loved it. Most of them had never seen a Western film. They related to Hermione and Ron and saw that they were "just like us; in school like us; with homework to do like us".

'That I found very moving. They were never allowed to see the outside world and be exposed to a world that isn't about the Great Leader .

'It was probably the first time they related to Western people in a normal way.'

But Miss Kim does not see much hope for the international pariah state opening up to the world any time soon, given what she saw of its system.

She said: 'I hope that things will open up even a tiny bit so the boys would be able to find out about my book - that's my biggest wish.

'But I am not that hopeful for real change because the amount of control I saw there was so absolute and so brutal, with no mercy.

'I thought the elites had it a better than everyone else. On the other hand they may have a had a bit more food and a bit more electricity but no one is spared in North Korea from the control of the military dictatorship.

'They are never allowed to move about freely in the country or exchange information. I don't see how they can rise up.

'I think change has to come from the outside somehow because I don't know what they can do from the inside.

'I really loved them and it broke my heart to see them living in that way, in that place.

'It was really a gulag, nothing else. It is the most inhuman thing, controlling people with fear.'