EU Counter-Terrorism Coordinator Gilles de Kerchove estimates several hundred youths from the bloc have been to Afghan-Pakistani tribal zones.

For Western counter-terrorism agencies there is another more insidious threat – online propaganda glorifying hatred and extremism.

“The Internet is an incubator of radicalisation,” de Kerchove said. “What is common to terrorists is dehumanising their victims, so they no longer feel the consequences of their actions. Giving them back a voice and returning victims to the forefront, showing the abominable consequences of terrorist actions, in a way, helps remove the ‘glamour’ from the terrorist act and in that way it is concrete counter-narrative policies that need to be developed.”

France is now reinforcing the fight against extremist indoctrination, online or otherwise, more aware than ever of the danger it presents.