Video report by ITV News Asia Correspondent Debi Edward
China's ambassador to the UK has been hauled to the Foreign Office in London to explain comments that Britain should stop interfering with an "internal dispute".
Meanwhile, Jeremy Hunt, the foreign secretary, has said that while there is no reason why good relations cannot continue, he could yet still hit Beijing with sanctions if it does not respect the 'one country, two systems' approach.
So, just what is Britain responsible for in Hong Kong?
What does 'one country, two systems' mean?
In 1984, British prime minister Margaret Thatcher signed a joint declaration with Chinese premier Zhao Ziyang whereby Hong Kong would return to Chinese control in 1997 under a 'one country, two systems' approach.
It was registered with the United Nations and guarantees to maintain a certain way of life and business until 2047.
The declaration said Hong Kong "will enjoy a high degree of autonomy, except in foreign and defence affairs" - in effect, Hongkongers would have their right to freedom of expression/assembly, have a guarantee of human rights, and to live under an independent rule of law.
Hong Kong business and trade would also not be answerable to Beijing.
What responsibilities does the UK still have to Hong Kong?
While Hongkongers enjoy more freedoms than people on mainland China, Hong Kong is not a democracy.
London insists the declaration is a "legally-binding" treaty; Beijing has described it as a "historical document" that no longer has "any practical significance".
The vast majority of Hongkongers who were British Nationals (Overseas) at the handover were granted automatic Chinese citizenship.
As such, while they are classed as British nationals, they are not, crucially, British citizens - so while they receive preferred status when visiting from Hong Kong, they do not have an automatic right of abode in the UK (unlike Britons living in Gibraltar or the Falkland Islands, for example.)
Former British prime minister Sir John Major said in 1996, on the eve of the handover, that Hong Kong would "never have to walk alone".
But, aside from an emotional attachment, the UK has little actual legal sway there.
And what happens to Hong Kong after its Basic Law expires in 2047 is not known...