i would just like to add , to this , being a street /urban photographer I have done alot of research on taking pictures /filming ..I would advise anyone being approached by police to film the conversation , it is perfectly legal and seems to keep police from lying to you , they have no right to look at your images or delete your images . When talking to the police , be polite and state you are filming for your own safety , ask them why they are talking to you , and if they say you are committing an offence , ask them to name the section of law that applies . Do not swear or shout or square up , this can be classed as behaviour likely to cause alarm of distress , finally do not go into conversation in a friendly manner as you may slip up , just ask " am I being detained " if the answer is no , then ask "am i free to go " ...keep asking the question until you get a favourable answer .
from an on paper legal point of view yes, however from the videos I have seen that followed this it kinda wound the cop up the wrong way and didnt go too well. personally I'd try and talk out of it off camera first, if I felt the cop was going to be a dick no matter what then yeah film it, but although perfectly legal it doesnt get things off to the best start. This is especially true in the context of exploring, yes we may not be breaking criminal laws, but trespass is still against civil laws we have no given right to be the places we go, and cops have every right to be suspicious of us. I'm not saying bend over and let them do as they wish but try and stay on a happy middle ground.