Try this if your stopped in your car and asked for your details I think you come unstuck. Any officer can ask you for your details at any time
Yes and no.
They are no longer allowed to ask for your details at any time. This law was repealed after the last war.
However, if they have good grounds for suspicion that you are in progress of performing something which is against the law, they can ask for whatever is required to prove that it was you breaking the law.
(i.e. if you are speeding, have a bald tyre or other item which might make your car of un-roadworthy condition, then name, address and driving license is suitable.)
I have a couple of reasons for not wanting to give my details to the police. I don't particularly like strangers anyway for a start.
The main reason why I do not want to freely give my information, is because of the mis-understanding above. The more people who believe the above, the further they stretch the boundaries.
The police are not above the law.
If you are in a public place they may ask for your details, but they may not demand them.
If they have good reason to suspect you of being in the process of breaking the law (or proof that you have just done, i..e shoplifting), they /may/ demand them, BUT, if practical, (and taking a photograph is not a high-speed chase), they MUST give the reasons as to why they are demanding them.
You are also allowed to refuse your details, if you do not wish to, or if you do not believe that their suspicions warrant the demand, but I am not suggesting that you do refuse. All I am suggesting is that the police are reminded that as a citizen, you are allowed to be anonymous, the police have no /right/ to your details.
As to the question about the fact that this helps stop terrorism.
Quite frankly, IF I were a terrorist, and I gave my name and address to a policeman and community support officer, do you think they would recognise it out of the several hundred on the watch list? It is a waste of time. Ok, so at the end of the shift, some poor SOB is going to type these details into a computer. My name is commonly miss spelt, I have probably around 5 or 6 different spellings in my wallet at the moment because I cannot be bothered any more to correct people. IF my name were on the watch list, (and if it was, would I really give my real name?), and if they managed to spell it correctly, then all they would know is that I was in London, on the south bank, on Tuesday. This information, without context, means nothing. Even with context it means little.