Hitherto, holding a British National (Overseas) passport has not even entitled you to register for the Registered Traveller service for clearing British immigration. For that, you would have needed the Hong Kong Special Administrative Region Passport, which was and is issued by China. These people's connection to Britain really is rather tenuous.
The Conservative Party won 317 seats in 2017, the hardcore Tory heartlands. Send 10,000 Hongkongers to each of them. Let there be a new town in each of those leafy shire seats which were blue on the map every time. Anyone could live there, but the original 10,000 inhabitants would be Cantonese. Who could object to that?
There are also longstanding ties between Hong Kong and Northern Ireland, where it was said for many years, before the recent mass revival of Irish there, that Cantonese was the second most widely spoken first language. The 10 constituencies that elected DUP MPs in 2017 might therefore share the load. Seven of those would easily be rural enough to accommodate a new town apiece.
So that is 327 constituencies altogether. Take out the 24 most urban Conservative ones and the three DUP ones with the word Belfast in their names, and then build a new town, initially for 10,000 Hongkongers, in each of the remaining 300. "Ye dare not stoop to less."
The reason why people who were now entitled to BN(O) status were not simply given British citizenship was because the Thatcher Government and its media supporters were having none of it. The mere suggestion led to claims that there would be opium dens on every High Street and what have you. How times change.
How, indeed. Margaret Thatcher's argument for the Falklands War was not that the Falkland Islanders were entitled to self-determination, but that they were "of British stock". Those were her words. Knowing its audience, the Falkland Islands Government seems to require that filming for domestic British audiences must scrupulously avoid showing the large number of inconveniently brown Saint Helenians who now lived and worked there.
But Britain has become ethnically diverse down to every ward, it has a large and rapidly growing mixed-race population, and there are people living in Britain from every inhabited territory in the world. In that globally unique context, then what does being "of British stock" mean, even before the arrival of a further three million Cantonese?
Leaving only the argument from self-determination. That could never have been used in relation to Hong Kong, since the Chinese were always going to have been entitled to their own territory back once the lease had run out. But it is unanswerable in relation to the Chagos Islands, whose predicament is not the fault of the Thatcher Government, but of the rancid right wing of the Labour Party from Denis Healey to David Miliband, and over whose homeland Britain has been found to have had no sovereignty by everybody and every body that has bothered to check.