A quick guide to peaceful attention
Interesting that most of the sentiments here call for remonstration of the figures of authority, but always from a third person perspective. It seems that "common" insistence of your civil liberties is no longer so common. Born after Brixton, Woodstock, or even the Gas Crisis, I was not "there" for the peaceful resistence movements against the police and military that were rampant then. But, I am a "Merikin" and "I am not a lawyer/solicitor", and I do have a bit of the passive resistence streak in me, so here is what I can think of off the top of my head:
1. Stay in teams. Camera phones are ubiquitous. If one person is photographing their environment (artistic or not!) legally, there is no right for any authority figure to restrain. The other person needs to record the event to give an unbiased account. Having several people do this is even more effective, and even better if many can do it *while being blatant about it*. Intimidation needs an air of secrecy to be effective. The thought that no one knows (or cares) is what propogates this attitude with the police. Knowing that their actions *are being observed publicly* will make them consider what they are doing "for the public good".
2. Distribute cheap disposible cameras in mass quanitites. You could probably even get some shops in on it (anonymously), as a "community building exercise". Having five, fifty or five hundred individuals taking snaps throughout a large public area could very well have the plods in apoplexy. And all legal, thank you very much.
3. The point of all this is to CALL ATTENTION TO YOURSELF AND OTHERS. Police propogate dissention against those they target by their very focus; if the police are "questioning" someone, everyone else is expected to not notice, or worse, expected to believe that "something happened". If you are stopped by a policeman, call out to your mate(s), "Hold on, this police officer ... officer (read off their name tag) would like to have a word with me. I will catch up with you later!" EVEN IF YOU ARE ALONE. If you really don't have anyone else there, calmly respond to their (inevitable) question of who you were calling to, "I thought I saw a friend of mine. Didn't expect them, but was going to ask them to lunch/dinner/pub". If you were mistaken and that was NOT who you thought, you are not to blame, eh? The point is other people will stop and look at what is happening. Even if they don't care, it forces attention onto the policeman's actions, and reminds them of that attention. If you know the person being "conversed with", ACKNOWLEDGE THEM. Stop, wave, can call them by name if you can. Make enough noise that others notice that you noticed them. Ask THE PERSON if it will be long before you can chat with them. By focusing the attention on the police and their actions and reminding them of their own individuality, they lose some of the "blue shield" mentality because you force them to think like a person and not a badge, even if only a minute.
Be polite at all times. By being a common, friendly British Citizen(r)*, you should show respect, but not blind obedience. They are *not* your betters, they are your *employees*, doing the job *you* pay them to do. If they ask for identification, respond calmly,
"As you are a police officer, I am sure you have been informed by your superiors of the various scams being commited by persons impersonating police officers lately. [I read about them in the Mail/Sun/etc,] and as per the suggestion of the Home Office's spokesman in the article, I humbly request that you show me proof of your position as well, [even if you are in uniform,] sir... Sorry, I can't remember which issue; it was a couple weeks ago."
By all means show your ID, BUT DEMAND THE SAME "COURTESY" OF YOUR EMPLOYEE. This reminds them that as a British Citizen(r)*, you are ON EQUAL FOOTING WITH THE OFFICER. Call them BY NAME and RANK throughout the event, respectfully, as a way of completely addressing the individual you are talking to, NOT THE BADGE. The only reason a police officer can hide behind a badge IS IF YOU LET THEM.
It may be helpful to memorize (Is there a TEST?!) parts of this: the Pledge of the Met.
Though it is obstensibly "only" for Met London police, it is a matter of professional pride of any member of the British Military (including the Police) to not contradict the words of a superior officer ON RECORD. Particularly, you might be interested in the bits on Page 2 where, "We will introduce ourselves," "we will tell you what is going to happen and why," and "We will give you a reference number and a contact number."
* Yes, it is becoming a registered title, as your personal information is being registered as we speak. By the by, I hereby release this comment posting to be reproduced at will for the purposes of educating the public, to the extent allowed by the Register.