A new visa initiative offering millions of Hong Kongers a pathway to British citizenship will go live on Sunday as the UK opens its doors to those wanting to escape China's policies to tackle dissent. From Sunday afternoon, anyone with a British National (Overseas) passport and their dependents will be able to apply online for a visa allowing them to live and work in the UK. After five years they can then apply for citizenship. The immigration plan is a response to Beijing's decision last year to impose a sweeping national security law on Hong Kong to snuff out large and often violent democracy protests. Britain accused China of tearing up its promise before Hong Kong's 1997 handover that the financial hub would maintain key liberties and autonomy for 50 years. London argued it has a moral duty to protect its former colonial subjects. "We have honoured our profound ties of history and friendship with the people of Hong Kong, and we have stood up for freedom and autonomy," UK Prime Minister Boris Johnson said this week. China criticised the visa offer. On Friday, it announced BN (O) passports would no longer be recognised as a legitimate travel or ID document. The move was largely symbolic because Hong Kongers tend to use their own passports or ID cards to leave the city. But Beijing said it was prepared to take "further measures", raising fears authorities might try to stop Hong Kongers from leaving for Britain. It is not clear how many Hong Kongers will take up the offer, especially as the coronavirus restricts global flights and mires much of the world, including Britain, in a painful economic malaise. But a BN (O) passport is available to about 70 per cent of Hong Kong's 7.5 million population. Applications for BN (O) passports have increased by more than 300 per cent since the national security law was imposed last July, with 733,000 registered holders as of mid-January. Britain predicts up to 154,000 Hong Kongers could arrive over the next year and as many as 322,000 over five years, bringing an estimated "net benefit" of up to £2.9 billion ($4bn). The BN (O) passport is a legacy of Hong Kong's return to China. Many Hong Kongers at the time wanted Britain to grant them full citizenship but China was opposed to the move. The BN (O) was a compromise, allowing Hong Kongers born before 1997 the right to stay in Britain for six months at a time, but with no working or settling rights. Now it has become one of the few ways out for Hong Kongers hoping to start a new life overseas as authorities conduct mass arrests against democracy supporters and move to purge the city of dissenting views. Stella, a former marketing professional, plans to move to Britain imminently with her husband and 3-year-old son. "The national security law in 2020 gave us one last kick because the provisions are basically criminalising free speech," she told AFP. Under the initiative, those hoping to move have to show they have enough funds to sustain both themselves and their dependents for at least six months. Hong Kongers already in Britain who are involved in helping others relocate say many of the early applicants tend to be educated middle-class people, often with young families, who have enough liquidity to finance the move. "Most people we spoke with are families with primary school or nursery age kids," Nic, an activist with a group called Lion Rock Hill UK, told AFP. Some Hong Kongers began leaving the city even before the initiative went live. Earlier this week Britain said about 7,000 people moved over the past six months under a separate Leave Outside the Rules (LOTR) system. They will also be able to apply for the pathway-to-citizenship visas. "The BNO is definitely a lifeboat for Hong Kongers," Mike, a medical scientist who recently relocated with his family to Manchester, told AFP. He said many Hong Kongers feared China might stop residents leaving the territory. "So it is better to leave as soon as possible," he said.