There is no national ID card in the UK so it would be impossible to enforce. There is no law saying you have to produce ID on request and "reasonable suspicion" only applies to a specific crime. The police can't just say that they have "reasonable suspicion" that you are committing an unspecified crime.
Does "reasonable suspicion" imply an unspecified crime? Does it have to be the case? Suspicion doesn't necessarily mean that it is the case, so as long as they can come up with reasons, it's fine, and they don't need to be correct, or at least they won't get "punished" for being incorrect. Is it wrong? I am just trying to gather more information. :D
Hmm, how do you generally prove identity in the UK?[1]
[1] Actually this is something I could easily look up on the Internet, sorry. I don't mean to waste your time.
Reasonable suspicion that you are breaking the law, or are about to break the law. They may be required to justify their grounds, i.e. what they suspect you of and why. They have been known to simply ignore those requests for why.
e.g. I suspect you of going equipped to commit burglary due to your stripey jumper, crowbar and bag with "swag" printed on it.
Proving ID is usually done via passport or driving licence. If you don't have those producing a couple from bank statement, utility bill or council tax bill is usually enough. I'm old enough to have got bank account without any requirement for ID at all. Yes, that means it can be a chain of circumstantial evidence rather than proof.
Basically the police can stop you if they have "reasonable suspicion of committing crime x" and they have to tell you which crime they suspect you of and why.
To prove who we are we can use a driving license or passport, if we have one. But there are many people with neither. In that case it's quite complex and usually requires a trustworthy person (doctor, lawyer, chartered engineer) who knows you well to confirm your identity.
It is very interesting, but how can people without an ID card vote, open a bank account or buy a ticket for a plane? How are they identified then? I guess there must be some equivalent of ID anyway. At least in Russia you need an internal passport even to exchange the currency if the amount exceeds $611 (which is great because earlier the threshold was about $250).
Pulling up an arbitrary UK bank, https://www.tsb.co.uk/current-accounts/faqs/identity/ shows many options to establish identity, including ones that don't require an identification card. Those under 18, for example, can use a National Insurance card or letter.
I don't know what domestic flights are like in the UK. From what I can tell, it's left to the airlines. Most (? all?) require some sort of id, and different airlines accept different forms. For example, FlyBe allows "Council issued bus pass" and "NUS card (National Union of Students)" and "Company ID card of nationally recognised company" - https://www.flybe.com/check-in/id-requirements .
In some countries (I'm thinking Australia, based on a podcast I listened to from a couple of years ago), domestic check-in is all automated and does not always require an id check. https://www.jetstar.com/au/en/help/articles/travel-identific... says "If you’re travelling with checked baggage on a domestic flight in New Zealand, you must provide ID." "Accepted ID types" include "Original or certified copy of a birth certificate", so "ID" is pretty broad.
To point out, voter impersonation - the sort of fraud which ID cards might solve - are very rare. See https://en.wikipedia.org/wiki/Voter_impersonation_(United_St... . The vote is private, so if there was an organized system it's difficult to verify that the vote actually went the correct way. It requires a lot of people in order to sway an election, and that sort of organization has a higher chance of being detected. The list of people who voted is public, so it's also possible to track down if they actually exist, and there's the risk that a impersonator will try to impersonate someone who actually voted.
If it's important to know who someone is, then it can sometimes be solve by using a chain of trust. For example, the bank might require that a current account holder in good standing be willing to vouch for me, even if I have no id. Or, I might deposit a lot of money but have limited abilities until the bank trust me more.
