The landscape of jihad is wildly different today from just a decade ago.
Then we had known centres of radical activism like the Finsbury Park Mosque and hate preachers such as Omar Bakri Mohammed and Abu Hamza.
All these preachers have now been removed from the country. But in many respects preachers and mosques no longer matter.
Much has been written about the role of the internet in the radicalisation of some Muslims.
The ubiquity of social media has meant that hundreds of foreign fighters now openly tweet, blog and Instagram their experiences.
They are easily accessible, providing a line of communication between aspirant jihadists and those already fighting.
This is why the British authorities are struggling to deal with this new form of preaching a message.
If you shut a Twitter account a new one can be opened. And then another. And another.
Scour the account of any Syrian jihadist from the West and you’ll find scores of questions from men back home asking how to emigrate, how to evade the authorities, what level of fitness is required – even whether hair gel is available in rebel-held areas.
One jihadist from Manchester issued a checklist of things for potential fighters to bring with them, including toilet roll, indigestion tablets and an iPad.
This has a uniquely powerful effect on those considering joining the fight.
It humanises the fighters and makes their dangerous journeys into Syria seem entirely normal. It seduces others into acting themselves.
Pictures also serve as a powerful recruiting tool.
British fighters not only publish cocksure pictures of themselves with guns, tanks and other hardware but also of everyday life – fighters playing football, swimming and enjoying feasts.
Closing accounts does remove a source of radicalisation but also destroys a rich vein of intelligence – watch enough accounts and you can assemble all sorts of information.
While the challenges of internet radicalisation are not unique, the dramatic rise of social media has made a difficult problem even more challenging.