The appearance of three British Muslims in the latest recruitment video for Syrian jihadists raises important questions about counter-extremist policy and the Prevent strategy.
Nasser Muthana and Reyaad Khan from Cardiff, and Abdul Rakib Amin from Aberdeen, are just another example of British Muslims who have left behind their conventional British lives to seek martyrdom and jihad in a foreign land.
The government estimates that up to 500 British Muslims have followed this particular journey to Syria. Most of them have joined ISIS, the putative Caliphate that nominally controls more Middle Eastern territory than the governments of Israel or Lebanon and, not satisfied with literally crucifying Syrians, is now marauding its way through Iraq on a campaign of medieval barbarism.
These British foreign fighters in Syria are not Syrian exiles fighting for the future of their country, as was largely the case with those who travelled from Britain to Libya during the 2011 uprising there.
Nor are they disadvantaged youngsters lacking a toehold in British society. Muthana was heading for medical school before he went to Syria. Khan is the holder of 12 GCSEs including two A* and six A grades.
These are British-born believers in global jihad, living the dream of every al-Muhajiroun and Hizb ut-Tahrir leaflet, apparently not bothered that most of their victims are fellow Muslims.
It has been said, rightly, that many, perhaps most, will return home - if they survive - and pose no threat to anybody in this country. But it is also inevitable that some of them will come back to Britain and try to kill their fellow citizens. Last month Mehdi Nemmouche, a French ISIS veteran, was arrested for the murder of four people at the Jewish Museum in Brussels. This is more likely to be a precedent than an aberration.
The large number of counter-terrorist arrests, charges and convictions since 9/11 are testament to the success of the Police and the Security Services in disrupting terrorist activity and preventing attacks. The 'Pursue' strand of counter-terrorism is generally working well, despite the failure to prevent the murders of Mohammed Saleem and Lee Rigby last year.
Less clear is the effectiveness of Prevent: that part of the government's counter-terrorist strategy that is supposed to dissuade young Muslims from falling for the seductive simplicities of jihadist propaganda. In recent years this has widened to include tackling extreme right ideologies, but radical Islamism remains its overwhelming priority.
Prevent has had some measurable successes, as would be hoped with upwards of £200million spent over six years. The Channel project, which intervenes with young people who have shown signs of supporting terrorism (and does so without criminalising them), has a good record. Lots of other projects have been successfully delivered to lots of appreciative audiences all over the country.
But the Syrian jihad is the first major crisis of radicalisation since the Prevent strategy was introduced in 2008, and it is difficult to look at the British contribution to this particularly brutal conflict without some uncomfortable questions coming to mind.
According to most estimates, Britain provides more foreign fighters in Syria than any Western country other than France. For sure, 500 people are a tiny fraction of the three million or so Muslims in Britain. But then so are the approximately 650 Muslims serving in the British army.
It seems that the moderating messages of Prevent struggle to match the savvy social media output of British jihadis in Syria, conversing directly on Twitter with would-be recruits across the UK or posting their latest YouTube videos.
Thousands of items of extremist content are removed from the internet every month at the request of the British government, but on its own this approach will not solve the problem. It is more important to compete directly with those who use the internet to spread extremist ideas, in the same internet spaces used by jihadist propagandists and recruiters.
This challenge is all the more difficult because some basic ideas in the jihadist narrative enjoy reinforcement from much wider public discourse. The notion that Islam is under attack, from Westerners, Jews, secular Muslims, apostates and others - and that in the right circumstances, violence is the appropriate response - is not restricted to ISIS YouTube videos or al-Muhajiroun leaflets.
For example, there is speculation about the role of Mohammed al-Arifi, a Saudi cleric who spoke in 2012 at the al-Manar Mosque in Cardiff that Muthana and Khan attended. Al-Arifi has called for jihad in Syria and described Shia Muslims as evil. He has claimed that Jews hide from Muslims to avoid being killed. He was banned from entering the UK earlier this year; but he had previously been invited to speak to UK audiences by (amongst others) the Federation Of Student Islamic Societies (FOSIS), Cageprisoners, iERA and al-Muntada al-Islami. And al-Arifi is hardly the only example of a preacher with vile views being given such mainstream platforms in this country.
The point is not whether Muthana and Khan were convinced to go to Syria by the specific sermons and speeches that al-Arifi delivered in Cardiff or elsewhere. It is that as long as mainstream organisations and institutions consider a man like al-Arifi to be an acceptable speaker to put in front of their audiences, no amount of Prevent spending or government messaging will cut off the supply of impressionable young British Muslims willing to kill and die for their jihadist fantasy.