(But note that searches under s.43 are still permissible. Section 43 at least requires that a police officer “reasonably suspects” that the individual concerned is a terrorist.)

In general, there would be no expectation of privacy in a public place or at a public event, but there have been exceptions – Campbell v MGN being one example from the English courts, and Von Hannover v Germany being one from the ECHR. Hence, there may be an expectation of privacy where one is doing something essentially private, even in a public place.

With regard to Data Protection, images of people are capable of being personal data within the meaning of the Act, and thus subject to the Data Protection Principles. But not all images of people will be regarded as personal data. It depends to some extent on the manner and purposes for which they will be processed. Also, processing data for the so-called “special purposes” – literary, artistic and journalistic, are exempt provided the processing of the data is “necessary” for one of the special purposes.
The issues are complex and there isn’t time or room for an in depth discussion of them here, but there is a lot of information on the Information Commissioner’s website. In particular, this guide shows how to tell if you are processing personal data: http://tinyurl.com/36g9ue
Look in particular at pages 11-12 for an example involving photographs.
The probability is that the kind of photographs you are talking about would not breach the Act, but it is hard to know without more detail. “general PR purposes” and “public places” are potentially pretty broad terms.

Being a keen photographer I carry my camera with me just about everywhere… on one occasion I was passing a school playing field (not the actual school.. and there was no reason to know that the grounds belonged to a school) anyway there was a group of people playing cricket on the field in the middle and I decided to take some pics… as I was doing so, two policemen on pushbikes came up to me and asked what I was doing (plus the question of did I have any of my kids playing in the field… which of course I didn’t)
Now the point here is they asked me for my details.. you know name address… and then let me go on my way… I honestly don’t see what I did wrong (which of course is not what the onlookers thought), and I did show the police the few pics I’d taken… my query is, was I under any obligation to show the police my pics (obviously I felt I was). They didnt’ ask, but supposing they did… could I refuse?… and what right did they have to ask for my details… given that I had not committed any offence…?
I took the pics standing on the pavement outside the perimeter fence… and there were adults also amongst the cricket palyers (probably not relevant).
Also there is the quesion of “why are you taking the picutres”…. does a human being actually need to have good reason or cause before he/she can legally take a picture in the UK..??… can you be arrested for not having a good enough reason…… I think this is a very important point… because most of the time I dont have a reason other than the fact that I like photograpy…(once an old bat came running out of her country home demanding to know why I was taking pics of her garden shed… oh the touble I had explaining to her)

I have researched the position regarding the right to publish photographs taken at public events and in public places and the position does not seem to be very clear. The question is simple: does an individual (or a company) require the consent of subjects of photographs in order to publish the photographs in magazines and newspapers? There is no intention of using the images for commercial exploitation in any way, merely for general PR purposes in various printed formats. There is also a possibility that the images would be used on the internet for the same reasons as the hardcopy formats, namely general PR purposes. A follow on question, which might raise slightly more issues is: does the copyright holder of the image have the right to store the images in an electronic image library for future use (either by it or other subscribers to the service) for future PR purposes, without the subjects’ consent or is consent required. And, is the position different for children with respect to both questions.

The Jules Mattsson incident appears, from the reports I have read, to be an example not so much of defective law as of defective application of the law. Or rather, no application of the law at all, since one police officer claimed they didn’t need the law to be able to stop photographers.

http://julesmattsson.wordpress.com/2010/06/28/the-romford-incident/

The Government’s application to appeal against the judgement of the ECHR in Gillan and Quinton v United Kingdom has been rejected. (This is the case in which the ECHR determined that stop and search under s.44 of the Terrorism Act 2000 infringed the right to privacy.) I mentioned above that the appeal was quite likely to be dropped by the new Government, but this is now academic since the ECHR has refused to hear it anyway.
http://tinyurl.com/37ub45x

However, some police officers seem to be determined to use the Terrorism Act in one form or another to prevent photography:
http://tinyurl.com/252qvqg

I had a minor run-in with a teacher last week while photographing (with permission) at an aircraft museum.

There were a huge number of schoolchildren there and many people taking photos of the exhibits from all angles and inevitably including some of the children in the shots, but the teacher decided to question me, probably because I had professional-looking gear.

My experience is written up on my blog at: http://martinliddament.wordpress.com/2010/07/01/show-us-your-papers/

I hope your campaign goes well. You have my full support.