With their stronghold of Mosul under fierce attack and Raqqa next in the frame, IS has intensified its global propaganda offensive, calling for more lone jihadis - 'lone wolves' - to slaughter civilians using knives and trucks 'plunged at high speed into a large gathering of unbelievers'. IS in Syria now direct attacks, giving lone wolves targets and instructions via encrypted apps that leave intelligence agencies in the dark. In this film for Panorama, reporter Peter Taylor investigates the escalation of this global phenomenon. He travels to the US to talk to the deputy director of the FBI and goes on patrol with the NYPD. He asks what the UK government can do to prevent radicalisation of young people and talks to Britain's most senior anti-terror police officer about what authorities here are doing to protect us in the face of this growing threat.