Unseen and undetected outside the "hermit kingdom", a quiet transformation is taking place. And it is one that North Korean officials freely acknowledge. "It is like a revolution," admitted Pak Jong-sok. A short, slender man with a cheery smile, he works for the ministry of culture, and was one of the two government guides assigned to accompany me everywhere I went during my stay. "Yes, it is going to be a big revolution, but I am not in it yet," he laughed.
Deep within the most closed society in the world, a cultural and technological change is brewing.
First, there are the mobile phones. Until six months ago, all foreigners entering the country were forced to hand over their phones to passport control and no North Korean was allowed to import a phone either. Now, every top government official in Pyongyang is waving his new toy around, like the kid in the playground with the cool new trainers. Everyone wants one - not so they can text their mates or find out the latest football scores, but because at the moment, a mobile phone is the greatest status symbol a North Korean can own.
Well, possibly. The owners of the brand new Mercedes that have suddenly appeared may disagree. Just 12 months ago, Pyong-yang's wide, straight highways were eerily silent. Six, often eight, lanes stretched across a road where just one lane would have been plenty. But things have changed. Aside from the new fleet of Mercedes, a steady stream of second-hand Nissans and Toyotas has also found its way on to the capital's streets. Pyongyang now sounds more like a city. It is still silent at night, but during the day, the low din of distant traffic can be heard at most points around town.
Travelling out of the city centre one day, I saw what at first looked like just another of those ubiquitous billboards in which proud and determined warriors stare into the middle distance beneath slogans such as "If the Party Determines, We Can Do Anything" and "Let Us Carry Out the Instructions Given By Kim Jong-il". Then I noticed the difference. This one included a car. A new car. Pak saw me looking at it. "Yes, that is our advert," he said proudly. There is no price on it, nor any indication of where one can purchase such a vehicle, but an advert it is. It has gone up since the start of the year.
Pak admitted that it was unlikely many people could afford actually to buy one. Which is perhaps just as well, because it appears to be taking Pyongyang residents - motorists and pedestrians alike - some time to adjust. Car drivers (all men; women aren't allowed to drive) have certainly not been taught a highway code of any sort. There are very few designated pedestrian crossings, and even these are marked with the faintest of white lines. Men, women and children amble across the road, seemingly unaware of the lump of metal speeding towards them.
Elsewhere, you can find evidence of the problems the country still faces: lack of electricity, which knocks out virtually all streetlights in Pyongyang during the night; the primitive ploughs pulled by oxen in the barren countryside. As for the biggest example of financial shortcomings, one has only to look up. Towering high above the capital's skyline, the Ryugyong Hotel stands as a testament to the folly of Kim Jong-il. Constructed more than a decade ago on his orders, the 105-storey, triangular structure was meant to be one of the finest, most luxurious hotels in south-east Asia. Today, it remains unfinished. One of the few cranes in the city stands at its peak, sitting on top of the concrete shell. Officials insist it will one day be finished, and are apparently looking for a foreign investor to pay $30m for it.
During the 1970s and 1980s, Kim Jong-il embarked on a series of major building projects intended to display the people's affection for his father. Stadiums, towers, statues - all were built in the name of Kim Il-sung, named "Eternal President" in 1998. The aim was to cement Kim Jong-il's position as successor to his father - something that was by no means assured. But ten years after the Great Leader's death, the Dear Leader commands nowhere near the level of respect that his father still does.
"You will see in your stay how much our people love our Great Leader and our Dear Leader equally," argued Pak. "We love them both the same." Except they clearly don't. Every North Korean is obliged to display their devotion to the leaders by wearing, every day, a small red lapel badge bearing the face of either Kim Il-sung or Kim Jong-il: for once in this country, the choice is entirely theirs. It is Kim Il-sung's face that beams out from almost every lapel; in ten days, I saw one person wearing a Kim Jong-il badge.
Further evidence was displayed at the opening ceremony of the Pyongyang international Spring Friendship Arts Festival - the event that I was allowed into the country to cover. When footage of Kim Il-sung was beamed on to the big screen, the 6,000-strong, predominantly North Korean crowd burst into uncontrollable applause. Moments later, when the rotund figure of Kim Jong-il waddled across the screen, the applause was far more reserved.
It could be argued that it is like comparing Winston Churchill with any prime minister since: whatever anyone else did, they didn't save Britain from foreign invasion. So, in some respects, Kim Jong-il has got it tough. The North Korean people believe that his father single-handedly ended the Japanese occupation before defeating the "evil US imperialists". Faced with that, how can he possibly match Daddy's "achievements"? Kim Jong-il manipulated his father's image, turning him into a godlike figure who freed the Korean people and led his country to greatness. He is carrying out his father's policies. And when these policies fail - as nearly everything has done since Kim Jong-il took over - Kim Il-sung will not be blamed. His son, however, will.
The dire state of North Korea's economy only exacerbates Kim Jong-il's problems. The fallout from the collapse of the Soviet Union - until its demise the largest donor by far of aid to Pyongyang - contributed to the famine that started less than a year after Kim Il-Sung's death and killed roughly 10 per cent of the population in the 1990s. North Koreans have known only financial hardship and food shortages during Kim Jong-il's ten-year reign.
Yet they do not blame him for their financial woes, at least not when speaking to journalists. Pak admitted that there were "financial difficulties", but pinned the blame on the US for "taking action against our socialism".
Nobody knows how or when the regime will fall. Nor does anyone know how a regime whose head of state is dead can collapse - how can a dead man be overthrown? What is certain is that the country is changing. Very slowly, it is opening up, encouraging tourists, and even allowing western journalists a little more freedom of movement. The introduction of adverts, the huge increase in numbers of cars and the inevitable spread of mobile phones are likely to have a big impact on the way North Koreans view the world. Whether the appalling state of the economy will help chip away at the people's faith in Kim Jong-il is another matter.