https://www.gov.uk/government/publications/british-national-overseas-and-british-dependent-territories-citizens
British National (Overseas) and British Dependent Territories Citizens
NOTE 1: Acquisition of this status was by registration and the BN(O) register is held by the Hong Kong Consulate General's Office.
NOTE 2: Children born between 1 January and 30 June 1997 were eligible to acquire BN(O) status until 31 December 1997
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