The BBC has broadcast a half hour documentary in London, a regional programmme oddly; it is not on YouTube, but will appear on BBC World News see:http://www.bbc.co.uk/programmes/n3ct1kws

The reporter is Raffaello Pantucci, of RUSI and he has written a summary on his website. It ends with, lightly edited, this and IMHO applies beyond the UK:
Clearly radical material disseminated online will fan the flames of ideas, and mean that groups like Isil will be able to maintain their notoriety and draw people to themselves. But it is the online manipulation that is turning these long-distance online relationships into terrorist attacks, and individuals like Junaid are able to manipulate people into launching attacks that are difficult to prevent in western capitals.

And while government can spend more money on staff and surveillance, when the style of attack is so individual, basic and diffuse, it becomes very difficult to maintain complete control.
Link:https://raffaellopantucci.com/2017/0...error-by-text/