Interesting contribution by Nigel Inkster, ex-SIS (MI6) and now with IISS:http://www.iiss.org/en/iiss%20voices...nd-brexit-c6ab

An interesting part:
Last week I featured briefly in the BBC's Panorama programme, which depicted in remarkable detail how ISIS had planned and orchestrated the complex, multi-phase Paris and Brussels attacks. As is always the way, many of my comments ended up on the cutting-room floor. But during my interview to camera I tried to explain the difficulties intelligence and security services face in dealing with transnational terrorist plots. Intelligence does not come in a regular flow and when it does come it seldom admits of only one interpretation, nor does it always lead inexorably to the next piece in the puzzle. Items of intelligence that in retrospect seem crucially important do not always seem so when they first come to light. Working in counter-terrorism is to see the world always through a glass darkly. Panorama showed that Europe's intelligence and security services knew they were facing a major problem, knew many of the actors involved and were in a desperate race with the terrorists. They were able to avert some of the plots, but could not pre-empt them all. I know from personal experience what it feels like to lose that race. Successful counter-terrorism operations involve a degree of luck. To talk of 'joining the dots', as if the complexities and uncertainties of such work can be reduced to the predictable simplicity of a child's colouring book, is not helpful.