Comment by cherryteastain

BN(O) is/was not a simple pathway to UK residence. As the wikipedia article says

> BN(O)s are British nationals and Commonwealth citizens, but not British citizens. They are subject to immigration controls when entering the United Kingdom and do not have automatic right of abode there

Things were different before the 1981 British Nationality Act but it's not too relevant for HK as the 1981 act is before the Sino British Declaration.