“THIS is a message to David Cameron,” begins the unmistakably British-accented rant, “oh slave of the White House, oh mule of the Jews”. Waggling a gun, his features obscured by a balaclava, the man calls the prime minister an “imbecile” for deploying armed forces against Islamic State (IS). His melodramatic, almost adolescent conniptions would be laughable were it not for what follows: the execution of five kneeling men in orange jumpsuits, accused of being British spies. The video, released on January 3rd, ends with a cherubic boy aged perhaps four proclaiming, in a southern English accent: “We will kill kuffar.”

Amid speculation about the man’s identity—newspapers named Siddhartha Dhar, a British-Indian—the tape elicited comparisons to earlier execution videos fronted by Mohammed Emwazi, a Briton known as “Jihadi John” who was apparently killed by a drone strike in November. Theresa May, the home secretary, told MPs this week that 800 Britons have now travelled to Syria and Iraq and about half have returned.

Britain’s anti-terrorism strategy is evolving. Despite new powers to monitor suspects and seize their passports, exit checks at borders and dollops of money, the spooks are having to set priorities. The state’s capacity to restrain every individual minded to kill for an idea has natural limits. So the government is turning its attention to the sort of non-violent extremism that creates conditions for the violent kind. In the process it is tacitly conceding an awkward point: most British Muslims abhor extremism, but a distinct minority is ambivalent. One poll in November suggested that one in five had at least some sympathy with young Muslims fighting in Syria (although, as many reports omitted to add, the question did not specify for whom).

Such thinking has been circulating in Whitehall for a decade, but the radicalising effect of IS and the exit of civil libertarian Liberal Democrats from the government in May have given Mr Cameron the impetus and political freedom to pursue it more forcefully (in Downing Street this is seen as one of the four main issues that will define his second term). So last July the anti-extremism “Prevent” programme was expanded to give public bodies like schools, universities and prisons a statutory duty to shield their charges and monitor them for signs of radicalisation. In a speech a month later Mr Cameron pledged more, adding: “Let’s not forget our strongest weapon: our own liberal values.”

This sleeves-up, ideological onslaught on Islamism is so sensible that other European countries want to emulate it. Yet it faces problems. Grandstanding by the government (blimpishly labelling as “British values” principles like tolerance that are in no sense autochthonous), as well as by some Islamic bodies (the Muslim Council has railed unhelpfully against Prevent) and the press (prone to lazy talk of “the Muslim community” as an indivisible monolith) steers British Muslims away from anti-extremism initiatives. Figures from the National Police Chiefs Council suggest that less than 10% of Prevent tip-offs in the first half of 2015 came from Muslims. Jahan Mahmood, a former government adviser, knows this mistrust: “People think: ‘Shit, who is this guy?’”

Suspicion among Muslims is matched by bewilderment among public servants. London teachers whom Bagehot asked about their new role said they felt overwhelmed; the complexity of modern British Islam is such that non-Muslim staff must resort to crude methods such as listening out for deaths in pupils’ families that might betoken youngsters on a foray to the Middle East. But often radicalisation happens online or outside the home (“If it is him, bloody hell am I shocked? I am going to kill him myself,” Mr Dhar’s sister said of reports that he might be the new Jihadi John). The authorities told one head that some pupils were at risk—but gave no names. Very little apart from ideology unites the jihadists, notes Innes Bowen, an analyst of British Islam.

The answer is for schools and councils to work with Muslim leaders. But which? Sifting out those energetically committed to fighting radicalism can be beyond well-meaning but strained local branches of the British state. Consider the Prevent grants that end up in the hands of ideologically contentious groups. Or the revelation in November that a community centre in north London was inadvertently hosting proselytising sessions for IS. Or the blind eye turned by local authorities to the recent infiltration of some Birmingham schools by Islamists.

Many of the more exciting anti-radicalisation initiatives are led by Muslims themselves and take place outside the Prevent framework. Mr Mahmood, wary of its brand, independently mentors young men. Alyas Karmani, a Bradford imam who has aptly compared the psychological function of IS guns to penis extensions, is similarly sceptical of Prevent. Abu Khadeejah, a Birmingham-based Salafist, posts theologically justified critiques of IS on his blog. Yet such types face intimidation and even physical danger. One anti-jihadist Muslim activist tells how a critic threatened him by drawing a finger across his throat.

Of pens and swords

What to do? In the short term the government should consider renaming and relaunching Prevent, a good programme with a bad reputation. But a generational struggle over ideas and minds requires a generational answer: a dramatic improvement in mutual understanding between different parts of an increasingly diverse society. That means more briefing on the nuances of British Islam for local authority figures (Ms Bowen’s book, “Medina in Birmingham, Najaf in Brent”, is a good start), arm’s-length liaison bodies for Muslim moderates uncomfortable about engaging with the state, efforts to reverse the decline of religious studies and better policing of fashionable but often unaccountable “faith schools”. One Prevent officer in London jokes that more students should be encouraged to study theology. Why not? In a battle of ideas, knowledge is the most powerful of weapons.