Sorry, did I put passport office? I meant nationality office.
The Windrush fiasco (and it has been) is not new. In the late 80s/early 90s, there was a similar outcry when the first generation of immigrants, virtually overnight, were informed they weren't British, and might have no legal right to remain. This was due to the fact that when they came over, their countries of origin were British, they held British Subject documents, as we all did before the BNA81 came into force) Many of them, upon their country's independence, became citizens of that country, and some of them duly lost their British citizenship. (in most cases, they didn't, but in the days before the internet and mass information, they didn't know, and panic ensued) The govt quickly added a clause to the BNA approving registration (which is generally a right, unlike naturalisation which is discretionary) for this group of people, as British Citizens.
I haven't read a lot about the Windrush people- but it's, I believe, connected. I guess we have a nastier govt now, than we did then, when Thatcher's govt dealt with the fiasco pretty sharpish. I do remember a lot of scaremongering in the press telling people they were going to be deported. That was never the case.