Like a lot other laws, this new law is vague, and thats the problem both for the photographing public and the police. It's more or less down to the judgement of the officer who is evaluating the situation and his or her mindset. And we all know that some cops are just... Well, A-------s ! Some are okay..

Governments also use terrorism as an excuse to pass draconian laws through without real debate, something that they have already done many times in the UK in recent times (remember the DNA database for all who have been arrested and had their DNA taken and kept on that database, even if they were wrongly arrested) ! 
And anyway, terrorism is not the major threat facing the world as they would try to have us believe. I'm more concerned about habitat destruction or population growth than terrorism, and so should all governments be, but they have no real answer to those problems because they are acceptable consequences of 'successful economc growth'. Governments fear any damage to that ideal, so thats why these pathetic laws get passed. I'ts fear that drives through these laws, fears that I do not share with the elected parties. Criminalising ordinary citizens who photograph public buildings is a trillion times less effective at stopping terrorism than (among myriad other things) invading foreign countries under the false pretense of trying to find WMD right !!!!!??

The UK is also the most 'watched' nation in the world via CCTV, so their is a real stink of hypocrasy here too !

Regards... Shaun.