I agree with your comments on potential terrorist action outside the security zone--it should be a concern, but really, those unforeseeable terrorist acts are the core of how terrorism works, aren't they? In which case, we are better off just to keep our calm and carry on, rather than go crazy over the possibilities--as this WW2 British poster advised:
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I was being sarcastic, not about your remarks, but about the whole G8-G20 security mindset that has reached a "logical" conclusion in the view that everything and everyone could be a weapon of terrorism and must therefore be removed from the area.