Further to my suggestion a couple of posts ago that terrorists do not carry around cameras with large lenses on tripods to carry out 'hostile reconnaissance' but are far more likely to use a mobile phone, it's good to see that the police already know this and have just published footage of a 'suspected terror cell' in action. I just hope that the same footage will now be used in police training.
See BBC article on terror cell photographers in action.
Aside from the size of the camera I would also suggest that the longer a photographer loiters with a camera in a location fiddling knobs, aligning tripod legs and generally doing things that seem a complete waste of time the more likely the person is likely to be a photographer. A terrorist would be someone who moves into position, whips out the camera phone, takes a quick shot and then moves off.
Hopefully such points are made in training because to the extent they are not, or not acted on in the field, it means that police (and just as worryingly) security people are getting distracted and simply missing the correct targets. One day it may cost lives.