Answer: Their 'expat' strategy.
And they are, were not alone in mankind's history since such a protocol is, has always been the basis of the greatest conquerors of humanity.
'Once a cheater, always a cheater'. But that sentence also means that some people not only never change but will remain who they think they are even in the midst of the most altering environment. It's kind of an original load of personality that they will never alter for if they did, they would not know anymore that they are the same person. That's a supernatural identity that trumps all other cards. I'd call it the sociopathy of national identity. Even if those people have completely changed their uses, and more or less live the same life of the naturals in the country they have landed, they remain in their mind Brits, Romans or Jews although not for the same reason, just add Muslims to the 'Jews' and so on.
Concerning most expats, they become more than often second class citizens. Not so for British. They are nurtured by the mother land more than those who live in it. And they become more English than the ones who stayed, more royalists than the queen, even after many generations. Same for the Jews even is they have turned completely non-jewish. Nationality and religions have been turned as weapons for conquest. The qualities destined at the origin to provide cohesion for a local group have become a strategy for domination.
Thailand: Fighting the "Superpower"