In 1982, Deng Xiaoping proposed to British Prime Minister Margaret Thatcher the principle of "one country, two systems" for Hong Kong. Everyone saw it as a brainwave – an excellent way to unite two mutually different systems in one country.
The formula recognizes the differences between capitalist Hong Kong and Communist China. Hong Kong was promised 50 years of autonomy. The concept was praised as a way for countries with deep political differences within their own boundaries to resolve conflicts peacefully. It was also supposed to be a model for the unification of Taiwan with China.
Now, halfway through the 50 years, many doubt whether it can last that long. The seven months of unrest in Hong Kong have thrown China's plan for Hong Kong into complete disarray.
The formula has become a dirty bomb in Taiwan.
Last month, Taiwan President Tsai Ing-wen declared at rallies: "We don't want 'one country, two systems". Over the past six months, the world has seen how the situation in Hong Kong has continued to deteriorate under 'one country, two systems'.
The evolution of the formula from an innovative solution into a damaged idea has much to do with the growing gap in expectations between Hong Kong and China. Beijing has redefined it, focusing on integrating the Special Administrative Region to the mainland, rather than preserving the city's uniqueness. Hong Kong, by contrast, fights to maintain its autonomy, as promised by the Basic Law.
For Beijing, Macau is the model SAR, which rejoined the mainland in 1999 under the same formula. It has a pliant legislature and civil society, "patriotic education" and has passed laws on national security. Beijing appointees have high positions in the government.
The concept's most difficult issue was – and is – democracy and the degree to which Hong Kong people can choose their own leaders and legislature. In economic issues, China has largely kept its promise of leaving Hong Kong alone.
After the military crackdown in 1989, Beijing began to see Hong Kong more as a national security issue than an economic asset. Since then, it has demanded the passage of Article 23, which has draconian penalties against disloyalty toward China, and the introduction of "national education", to have students learn more about and love China, rather than Western values promoted in the past. It has passed successive measures to restrict the elections promised by the Basic Law.
Before the handover, the official members of the Executive Council and the Legislative Council proposed that 50 percent of Hong Kong's legislature be directly elected by 1995 and 100 percent by 2003. Beijing rejected this.
In 1996, a 400-member selection committee chose the city's first post-handover chief executive, Tung Chee-hwa. In elections in 1998 for a new legislature, only 20 percent were directly elected.
In April 2004, the National People's Congress ruled out universal suffrage before 2012, even though the Basic Law states: "the Chief Executive should be chosen by universal suffrage". It took the decision in the wake of Hong Kong's first major march of about one million people against the enactment of Article 23.
In recent years, Beijing has been intervening more directly in Hong Kong affairs. The Central Government Liaison Office openly ran the local elections, giving instructions, mainly via the pro-Beijing Democratic Alliance for the Betterment and Progress of Hong Kong.
In 2014, China further tightened the election rules. The NPC proposed that the 1,200-member election committee choose two to three candidates for chief executive in 2017. The winner would be chosen by universal suffrage and "appointed" by Beijing.
A majority of the population vehemently rejected this. They saw it as Beijing's order to curb the democracy promised to Hong Kong. This led to the Umbrella Movement. It ran for 79 days from September to December 2014 and attracted 200,000 people. They demanded full universal suffrage.
The Beijing and Hong Kong governments did not give way. Since then, they have ruled out political reform and said they must concentrate on livelihood and economic issues, despite seven months of the biggest street protests since 1997.
On Monday, in his first remarks in Hong Kong since becoming head of the Central Government Liaison Office, Luo Huining said nothing about political reform or universal suffrage.
So, 23 years since the handover, there has been negligible democratic reform. Perhaps Deng, who created the formula, believed that, as China became richer and more powerful, it would be more flexible and able to give Hong Kong people more of what they want.
This has not happened. The mainland has indeed become richer and more powerful but its government has become more centralized and increasingly restricted the space given to civil society. The gap between what the majority of Hong Kong people want and what Beijing is willing to give is becoming wider.
The protests have shown how little autonomy the SAR government really has. Paralyzed, the chief executive can take no major decisions but waits for orders from her masters in Beijing.
Some analysts say that such a clash is inevitable, as two completely different systems have inherent tensions, fueled further by mutual suspicion and dislike.
Many worry that, as 2047 approaches, "one country, two systems" will look substantially different to what it once promised.