"We're in every corner of society, watching, to see if there is anything suspicious which could infringe on the national security law," former banker Innes Tang tells the BBC World Service. When the UK returned Hong Kong to China 28 years ago, internationally binding treaties guaranteed the city's rights and freedoms for 50 years. An additional security law called Article 23, voted in last year, has further tightened restrictions. Hong Kong's authorities have set up their own national security hotline, receiving 890,000 tip-offs from November 2020 to February this year - the city's security bureau told the BBC. There is a danger the National Security Law will be weaponised, he says, with people saying: "If you don't agree with me, I accuse you of infringement of the national security law."