Britain should have offered British passports to every Hong Kong back in 1984, when Margaret Thatcher decided to return the territory to China without having consulted the people of Hong Kong about it. I'm not sure how many people would move to Britain under Johnson's offer now, or exactly who they'd be - I think most of the money-men would either already have foreign passports, be able to qualify for them easily, or not be too bothered about Beijing tightening its grip. Canada and Australia seem to be the preferred destinations these days anyway.