The obscure little "Qiao Xing Ju" (Happy Bridge) restaurant, situated on a tree-lined avenue in Beijing, has a rather intimidating atmosphere, perhaps because the proprietor does not welcome strangers. This is hardly surprising, as it is run by the North Korean government, and indeed the socialist-style karaoke has not much to recommend it, except to those who like patriotic songs about sacred mountains.
Among the regular patrons are North and South Korean diplomats, who do sensitive business over plates of kimchi in the private booths upstairs. The Korean staff is bused in daily from the North Korean embassy compound, and discouraged from talking to customers.
However, not long ago a Chinese friend had a brief conversation with a waitress. "Do you like Mao Zedong?" he asked. "Of course," she replied.
"What about Deng Xiaoping?" She grew embarrassed. "Why do you make fun of me?" she said. "Of course not."
This brief exchange spoke volumes about North Korean communist indoctrination. Mao was a true believer, but Deng Xiaoping, who opened China and introduced limited capitalism, was a heretic.
Even for a North Korean to contemplate Chinese-style re forms was a serious offence, as Lee Min-bok, a former research worker of North Korea's Science Academy, told me last week in Seoul. He defected because he fell foul of the ruling Workers' Party after writing to Kim Jong-il to say that breaking up collectives, as in China, increased food production three-fold.
Against this background, when Kim Jong-il came to Beijing two weeks ago and told President Jiang Zemin that "China's policy of opening up to the outside world is correct", it was a bombshell. In the communist world, such a comment would not be made without long preparation.
If the North Korean leader now believes opening up is the correct policy, then the summit with South Korea's President Kim Dae-jung this week was always going to be a success. Opening up means devising new economic models with some forms of private ownership, such as joint ventures. It means attracting outside investment on a large scale. South Korea is the only country in a position to play a leading role. It has the disposition and the resources, and a common language and culture.
There are well known reasons why Kim Jong-il and his comrades decided to jettison their treasured self-reliance policy of juche, which allowed them to retain complete control by closing the borders and indoctrinating the 23 million population.
The economy has failed and North Korea is dependent on foreign aid to survive. The army has been outclassed by enemy technology. Production of grain, coal, petroleum, fertiliser and electricity steadily contracted throughout the 1990s. The light water nuclear reactor project will not be completed until 2006, meaning urgent help in filling energy needs is needed from outside.
Massive investment from the South was the (unwritten) quid pro quo for the North's summit promises this week to help reunite divided families and end hostile acts and words.
But to compare the Pyongyang summit as some have done, most notably the Japanese Prime Minister, Mr Mori, to the fall of the Berlin Wall is to make a false analogy. The Berlin Wall fell because the collapse of communism in the Soviet Union had led to political and social turmoil in East Germany, and the flow of East Germans leaving for the West had become unstoppable.
There is no sign of such serious political turmoil inside North Korea. The carefully orchestrated crowd scenes laid on for the summit were an expression not of spontaneous joy but of absolute control. The prospect of a mass exodus is remote.
Tens of thousands of Koreans have escaped across the border with northern China in recent years, but it is not an attractive option even for desperate people. If they are caught by Chinese police they are forcibly returned to North Korea, despite protests from the UN High Commissioner for Refugees (UNHCR) that they face severe reprisals and are therefore de facto political refugees.
This is an embarrassment to China, which is already burdened with supplying cheap oil and grain to its starving neighbour. Now, with Pyongyang needing the patronage of a big power to go into talks with US-backed South Korea, China finds itself able to turn the situation to its advantage.
Washington has portrayed North Korea as a dangerous rogue state to promote the development of a theatre missile defence system. Fearing that this will give the US an even bigger strategic advantage, China and Russia have argued that such a star wars system would disrupt the world's anti-missile defence arrangements. China is especially concerned it would be used to cover Taiwan.
Beijing and Moscow can now scuttle the US argument by helping North Korea become a respected and legitimate international partner. This is one of the reasons why President Putin of Russia has decided to visit Pyongyang next month. Another is that it brings Russia into play again in the Korean peninsula.
It is also in the interests of all the main regional powers, the US, Russia, China and Japan to coax North Korea out of its poverty and totalitarianism to lessen the chance of war.
Pyongyang is already reaping the rewards of its international makeover. China is giving substantial new aid donations and the US has lifted several sanctions and sent a new consignment of 50,000 tonnes of wheat.
The most serious flaw in the Berlin Wall analogy is the assumption that wealthy South Korea is about to swallow up impoverished North Korea. South Korea's President Kim Dae-jung categorically said before the summit that this is not an option.
The text of Wednesday's agreement between the two Kims did not in any way envisage a unitary state, but mentioned vaguely the common elements of federation. Korea's neighbours are not unhappy about this. They are nervous - particularly Korea's traditional enemy Japan - about a new power of 70 million people emerging in Asia that might seek to employ nuclear weapons in its own defence.
Diplomats in Seoul say that one of the main aims of the South Korean government in starting the summit process is actually to prop up the regime in the North, not to undermine it. South Korea could not cope with a mass refugee crisis if the North collapsed in chaos. They are terrified about weapons of mass destruction falling into the wrong hands in the event of a crisis.
Nor could Seoul afford the estimated $1 trillion bill - a figure based on the German experience - to pay for the economic reconstruction needed to take North Korea into its system. Living standards in the North are a tenth of those in the South, a disparity twice as great as between East and West Germany.
The cost is only bearable if there is a gradual coming together. This has already started in a small way, with 145 South Koreans investing in modest enterprises in recent years. What is most likely now is that South Korean chaebols, the big family-owned conglomerates that are the foundation of its industrial success, will get in on the act in a big way. "The pace of South-North collaboration in all aspects of industry will increase drastically," said an official of the Ministry of Commerce, Industry and Energy in Seoul.
The 130-strong delegation President Kim took with him to Pyongyang had more businessmen than bureaucrats, all of them eager to invest in the relatively well educated, low-wage north. They discussed investing in new roads, railways and port facilities.
The Hyundai Group, which has paid $1 billion for the exclusive rights to ferry tourists to North Korea's scenic Diamond Mountains, is planning a huge industrial complex on North Korea's west coast, as well as hotels, golf courses and ski slopes and its founding patriarch, the North Korean-born Chung Juyung, will travel to Pyongyang next week to promote group investments.
Executives from 10 electronic firms and a delegation from the (South) Korean Federation of Small Businesses will follow. Samsung Electronics plans a one billion dollar production complex.
The main impediment to rapid investment, economists say, is a lack of cash, as many companies are burdened with mountains of debt since the 1997 Asian economic crisis.
Despite the evidence of a revolutionary rethink in North Korea's national ideology, critics say it is hard to see rapid change in the country's political state. Secrecy is an obsession, and co-operation with willing international friends is often minimal. Oxfam pulled out last year, and aid agencies complained jointly that they were not allowed to verify where their assistance was going. Also there are no mechanisms to protect investments or the physical safety of foreign business people.
Similar challenges faced China after the Cultural Revolution, and it is likely that the North Korean diplomats in Beijing will now be inviting Chinese officials to the Happy Bridge restaurant to pick up a few hints on how to cope with the coming changes. They might also instruct their waitresses in future to sing the praises of Deng Xiaoping rather than Mao Zedong.