Roughly 200,000 Hong Kong citizens are set to move to the UK after Boris Johnson offered them a route to citizenship, according to Foreign Office estimates.
The Prime Minister unveiled the measures, for which three million residents Hong Kong are eligible, after China brought in a draconian security law in Hong Kong.
The law makes it easier to punish protesters and reduces Hong Kong's autonomy.
The Foreign Office has a working estimate that 200,000 people in Hong Kong are likely to take up the British Government’s offer and move to the UK.
One source told the Financial Times that the exact number was in a state of "flux", with an average of 180,000 expected. Another said the department predicted that more than 200,000 would move.
The Conservative MP Alan Mak said Hong Kong citizens moving to the UK would bring a "very big boost" to the economy.
Mr Johnson has called the security law a "clear and serious violation" of the joint declaration between the UK and China over Hong Kong's future.
Speaking at Prime Minister's Questions on July 1, he said: "We made clear that if China continued down this path we would introduce a new route for those with 'British National Overseas' status to enter the UK, granting them limited leave to remain with the ability to live and work in the UK and thereafter to apply for citizenship, and that is precisely what we will do now."
The move prompted Beijing to accuse the British Government of "gross interference in China's internal affairs".
Meanwhile, it has emerged that Nathan Law, one of Hong Kong’s most prominent pro-democracy activists, has fled Hong Kong for London.
Mr Law said on Twitter: "With my backpack and small luggage in hand, I boarded my night flight. I had no idea what future awaited me. Only one thing seemed certain. My destination: London.
"There’s always one message I have: Hongkongers will never give up. We aren’t fractured. On the contrary, we're well-equipped to face the next difficult battle."
Mr Law, 27, rose to prominence during mass protests in 2014 and co-founded the Demosisto Party. The party disbanded when China imposed the new security law.
Watch the latest videos from Yahoo UK