It's worth recognizing that that was the case because China told the British that they would invade HK if the British gave them full self-determination.
That's not true. Britain ruled Hong Kong for over a century without introducing democracy. The governor was appointed by the UK Foreign Minister, the legislature was appointed by the governor, and most of the high administrative posts were held by Brits. Chinese people were treated as second-class citizens, and of course had no say in government. The UK only began introducing any democratic elements once it became clear that they were going to hand over the city to China.
