https://www.gov.uk/government/publications/british-national-overseas-and-british-dependent-territories-citizens
British Dependent Territories Citizens who did not register as British Nationals (Overseas)
Ethnic Chinese Former ethnic Chinese Hong Kong British Dependent Territories Citizens (BDTCs) who did not register as BN(O)s ceased to hold British nationality on 1 July 1997 and became Chinese nationals. An applicant who was a former BDTC should be advised to contact the Chinese Embassy for information and an application form for a Hong Kong Special Administrative Region passport.