When the first Islamist terror attack in Britain took place – the horror of 7/7 – suicide bombs were the means and training abroad the method, or part of it: mobiles were cruder and Twitter didn't exist. Much has changed since the day when I sat in David Davis's office (he was Shadow Home Secretary at the time, and I was a Conservative MP) scribbling lines for his response to Charles Clarke's Commons statement. Osama Bin Laden is dead, his Al Qaeda network is smashed, and rookie terrorists aren't necessarily put through their paces in Afghanistan or Pakistan: one of the last domestic British victim of an attack was an MP, Stephen Timms.
His attacker, Roshonara Choudhry, was self-radicalised towards extremism and violence: that's to say, she'd been swayed by videos of Anwar al-Awlaki, an American Al Qaeda terror cleric. Choudhry embodied the danger which the security services had warned about – the "lone wolf" who would strike without a supporting network: the Islamist equivalent of Anders Breivik, the Norwegian fascist terrorist. It is too early to tell if the two terrorists who so foully murdered a soldier yesterday in Woolwich were also isolated and home-grown, or part of a wider network – and recent arrivals in Britain.
It's also unclear whether they were converts to the Salafist-Wahabi strand of Islam – of which Al Qaeda is the one of the most violent manifestations – from a traditional Islamic background or from outside the religion altogether. But what is certain is that beheading British soldiers has been an aim among Al Qaeda-inspired fanatics for some time. For example, Parvix Khan from Birmingham received a life sentence in 2007 for plotting to behead a soldier "like a pig". Today's terrorists were taking a well-trodden path – albeit one with a peculiarly and sickeningly modern or even post-modern end: one was videoed by passers-by mouthing propaganda.
The speed at which the film was disseminated, the frenzied reaction to the atrocity on Twitter, and the sheer pace of modern news all point to danger. Terrorists aim to provoke reprisal attacks – as those who launch them would term them – on innocent people: in this case, Muslims. As one of yesterday's terrorists reportedly put it: "We want to start a war in London". I wondered when I was an MP how many Al Qaeda terror assaults it would take to spark attacks on Muslims and mosques. Or what the consequence of a prolonged Israeli incursion into Gaza would be for British Jews – or the effects of war between India and Pakistan on the streets of London or Birmingham.
The barbaric murder of a member of the armed forces will sicken and anger the overwhelming majority of the British public. As I write, we cannot know that yesterday's horror will not repeated, that the murderers were not acting alone, or that further assaults of a similar kind will not be attempted. However, we can be sure that the hearts of British Muslims sank at yesterday's news. For them, the return of Islamist terror to Britain means more journalists in their neighbourhoods, more scrutiny of their circumstances, more awkwardness (at least) in the shop or office or playground – and more antipathy towards their religion.
Most will recognise, none the less, that Britain has been a warm home for Muslims – just as it has been for successive waves of immigrants – and many will acknowledge (though more frequently in private than public) that the driving cause of yesterday's bloody horror on the streets of Woolwich isn't deprivation, or inter-generational tension, or even foreign policy, but ideology: the belief that the problems of Muslim-majority countries are caused by western democracies, and that the solution lies in an Islam unrecognisable from the traditional, classical form – one in which that religion has been twisted into an totalitarian ideology like communism or naziism.
Britain is only a part of the worldwide theatre on which the conflict between Islamism and its enemies – that is, nearly everyone else, including Sufi Muslims as well as western democracies – is being fought. Governments must thus recognise that there are limits to what policy can achieve. Withdrawal from Iraq and coming withdrawal from Afghanistan have not ended terror, as we saw yesterday. The security services will not halt every plot, though they have stopped many since 21/7. There is no evidence that initiatives such as last Government's Prevent policy, on which it staked so much, delivered hard results or value for money for the taxpayer.
Islam is compatible with democracy, Islamism is not – but politicians have neither the knowledge nor the mandate to help shape "a British Islam". Perhaps all they can do is run an effective security strategy, and make limited political progress. The latter would include recruiting more Muslims into the armed forces – there were about 600 in 2010: one of the biggest barriers to recruitment, according to Shiraz Maher's Ties That Bind, is that young Muslims are unaware that the opportunity to join is there at all. (Maher's pamphlet for Policy Exchange tells the story of how hundreds of thousands of Muslims fought for Britain in two world wars.)
Above all, government can grasp that violent extremism has its roots in extremist ideology – which infects the minds of failed young men like a virus, and lends them a sense of identity and belonging. Theresa May is working hard at keeping preachers who share that ideology out of the country – though CLG had not, when I last enquired, set out its counter-extremism policy (for which we have waiting for over a year). There are still conspicuous problems, but this is not the time to return to them. Rather, it is one to think of and pray for the friends and family of a soldier murdered while unarmed on the streets of Woolwich. And to add that attacks on mosques or Muslims in response betrays the values of the country he served.