Pete, Ive spent decades in and around London and our big cities, I've felt the ground shake and have ducked to avoid broken glass as IRA bombs have gone off - I've seen the aftermath in other Country's of war - I've seen how quick a train carriage emptied when a darker skin employee sat with me after the London bombings - the fact that he was my QS didn't do anything to stop folks worrying.
Back when the IRA were active over here normal life didn't stop, folks weren't scared to go out, generally this Country's spirt carried us through, we just assumed (and where right) that everything possible was being done to prevent these attacks.
Things changed when someone's skin coloured could be used as a point of suspicion, certain sections of the community jumped on this to suit their own agenda.
These days we don't appear to be able to trust those who tell us that everything possible is being done to prevent these attacks, we appear to feel better if we can physically see something, such as armed police or the army, on every corner.
The attacks in other Country's haven't been stopped by arming plod, its a flawed concept - granted it might make some feel more secure, but its simply depriving areas of resources, such as intelligence, which is the real way to properly defeat ISIS.
Also giving those disaffected enough to join a purpose in life in this Country will starve the radicals of new cannon fodder.