Thanks for bringing this to my attention gradient. I hadn't realised it had become so hazardous for photographers here in the UK. Like inshaala , I can appreciate that in certain areas and situations that we as photographers find photogenic ( e.g. transportation, power supply, defence, large crowds, tall buildings, etc) the police are only being precautious in performing their duty.  Although, I would agree that both parties  should be fully aware of a photographer's rights, both be civil and courteous, and not be heavy handed or threatening in their approach to each other.  I guess there would also be some sort of complaints procedure, should an officer overstep the mark.  Anyway, thanks again, I'll maybe go and request permission beforehand in certain situations and save myself some grief in future.