Boris Johnson is ready to open the door to nearly three million Hong Kong citizens if China imposes a new security law that critics say would rob the territory of its autonomy. The Prime Minister, writing in The Times, has offered to make what he says would be one of the "biggest changes" in the history of the British visa system to allow 2.85 million Hong Kong citizens the chance of fully-fledged citizenship. The move, which represents a dramatic escalation in the stand-off between the UK and China, would put Hongkongers "on the route to citizenship", said the Conservative Party leader. China's ceremonial legislature, the National People's Congress, endorsed a security law for Hong Kong earlier this week that has strained relations with the UK and the US. The law will alter the territory's mini-constitution, or Basic Law, to require its government to enforce measures to be decided later by Chinese leaders.