China bluntly told Britain on Wednesday to refrain from further interference and London summoned Beijing's ambassador for a dressing down in a rapidly-escalating diplomatic feud over Hong Kong.
The protests sweeping the former British colony have also revived tensions inherent in the two sides' historic agreement on the global financial hub's handover to Chinese rule 22 years ago.
Hong Kong was meant to continue enjoying broad freedoms under the one country, two systems approach first adopted by China in the 1980s.
But fears and frustrations over Beijing's gradual tightening of those rules spilled over into mass demonstrations against a now-stalled draft law on Hong Kong residents' extradition to China.
They also saw UK Foreign Secretary Jeremy Hunt - one of two candidates to become Britain's next prime minister - take the global lead in condemning China's entire approach to its special administrative region.
Hunt called on Beijing not to use the protests as a pretext for repressions and warned of serious consequences if China breaches the commitments it made to London decades ago.
His comments provoked a cascade of condemnations from China that began with its foreign ministry in Beijing and continued with its embassy in London.
He seems to be fantasizing in the faded glory of British colonialism and in the bad habit of gesticulating while looking down on other countries' affairs, Chinese foreign ministry spokesman Geng Shuang told a regular briefing in Beijing.
I need to re-emphasize that Hong Kong has now returned to its motherland.
The diplomatic offensive raged on at a hastily-convened press conference in London by Chinese ambassador Liu Xiaoming.
I do hope that the British government will realize the consequences and would refrain from further interference from further damaging their relationship, Liu said.
He spoke moments before being summoned by the Foreign Office for a private meeting with UK diplomatic service chief Simon McDonald.
Liu was informed that the comments made on UK policy towards Hong Kong by the Chinese ministry of foreign affairs spokesperson were unacceptable and inaccurate, a UK Foreign Office spokesman said.
The sides' relations are turning into a hot-button issue in London because of both Britain's impending exit from the European Union and the imminent adoption of 5G technology.