The only logical response to this last series of postings is "How bizarre!" Talk about down the [white] rabbit hole. My father emigrated to England from The Netherlands in 1915 at the age of three. He was educated and grew up there, worked and paid taxes there, married a Brit, bought a house, fathered and supported two daughters through to the end of higher education. He spoke perfect English (as well as quite a few other languages). He had no desire to become a British citizen, although he had some strong political views but could not vote, and never did. There was a wee glitch about his right to residency in 1945 – as there was for many – but that was quickly sorted out. He died in 1979 so the EU, the Schengen agreement and so on really did not affect his life.
Sometimes immigrants want to become citizens of their new country; sometimes they don't, especially if it means relinquishing their original citizenship. It doesn't mean that they haven't become a worthwhile participant in their new country's society. I haven't decided yet whether I shall apply for citizenship in NZ. I have residential status and cannot apply for citizenship for another couple of years. It's quite an expensive process here. Does anyone know what it costs in the UK? Here, we have to swear an oath to the Queen and her successors but I don't think anyone, even our recently resigned right-wing prime minister, has suggested an oath on New Zealand values.