// that's like saying a black person can never be British //
I don't think it's quite the same.
It's like saying a Kenyan black person can't be British.
A British black person can be British.
A Kenyan black person can't be British, because they are Kenyan.
A Kenyan black person's children could be British, if they were born in Britain.
The exception to all that is, of course, to become formally naturalised in ones country of choice. But, as the essence of this thread is about skipping formal naturalisation procedures, I don't suppose that would be relevant.