Just wondering, I’m helping some students with their visa extension applications here at the uni’ and some of them have police registration documents. Students of some nationalities have a few days after arriving within which to register with the police, they then get a nifty laminated sheet upon which is entered every visa or address change during their stay.
Some nationalities, e.g. Afghan or North Korean, would seem to be nationalities the police might wish to keep an eye on. But others on the list, Kuwait, Peru, Argentina, Brazil, Cuba, Egypt seem rather innocuous. Some, like Nigeria, don’t appear on the list but are nations from which a fair deal of illegal immigration occur. Is there a reason why some nationalities must register with the police in the UK and others not?
These things are rarely to do with current political situations and are more to do with visa agreements between respective countries. I suspect it’s got something to do with Visa regulations - Nigeria, being part of the Commonwealth, may have a different visa arrangement with the UK than other, non-Commonwealth and non-EU countries.
As visa agreements are often dealt with on an individual country basis (e.g. the US isn’t part of the Commonwealth or the EU but has it’s own agreement with the UK to waive visas) then it’s often difficult to apply a simple answer to your question.
Just speculation, but a lot of this stuff can be reciprocal: some those governments had some sort of diplomatic spat with the UK, so they imposed restrictions on UK citizens, which were then reciprocated here.