It's been nearly a week since the UK weathered a major terrorist incident in Westminster - and the fallout continues apace.
Khalid Masood drove into a throng of pedestrians on Westminster Bridge, killing three people, before fatally stabbing a police officer, PC Keith Palmer, and being shot dead.
The event is just the latest in a string of terrorist atrocities to devastate Europe in the last couple of years, and many of them have their roots in a handful of towns and cities which have emerged as hotbeds of extremist activity.
Drawing on the investigation into Masood, and previous probes into terrorist attacks across Europe, we've drawn up a map of the five most prominent centres of terrorism and extremist activity in Europe.
Each of the five areas has produced a significant amount of terror-related arrests, as well as seeing a number of people leave to fight for Isis in Iraq and Syria.
Check out the gallery above.