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 .