Prof Greg Barton says Numan's (Islamist) radicalisation was very fast, and I accept that. However, there seems to me, on reading this, that there was ample evidence for those close to Numan to be very concerned indeed. As adolescents mature, they can change rapidly; I personally don't find Numan's story surprising (apart from its miserable end). Rapid changes in thought processes are very common in adolescence, if not towards Islamist radicalisation then certainly to other forms of radicalisation. If rapid Islamist radicalisation is currently rare that may well change in the future.
How not to establish rapport
I remember when I was 18; if I was asked to report to a police station I would have felt extremely uncomfortable - it's hardly neutral territory to establish "rapport" is it? Instead, they could have suggested meeting for a kebab, or something like that, and worn plain clothes.
The "war on terror" that will not end while we continue to make the same errors
As for the wider, ever deepening series of terrorist tragedies in Europe, Turkey and elsewhere: I first published on these issues in 2000. My opinion then was that global inequality is so high that privileged populations should expect a backlash. I argued then, and I have argued many times since, that reducing inequalities are the best way to ensure the sustainability of civilisation. I hear and read occasional echoes of that view from Muslims, but such opinions, uttered by non-Muslims, are virtually never heard on mainstream media, and not much in academia, either. Paul and Ann Ehrlich's book "One with Nineveh" is a notable exception. An essay by Thomas Piketty puts an interesting twist on this, but I believe his points as reported (inequality in the Middle East) are only a minor contributing cause. (Note Piketty's blog is French, my comments are based on a commentary.)
While we in the rich countries continue to support the use of drones and other forms of extreme violence, all too often killing civilians, and even striking an MSF hospital in Afghanistan, we cannot expect victims to consider us as benign. They will try to strike back and they will attract sympathisers. We need to at least move in the direction of a fairer world, not an intensifying fortress world.