Until last week's attacks in Paris, the assumption had been that homegrown jihadist extremism was no longer operationally capable; that any attack would be a pale shadow of what al Qaeda was once able to plan in the heart of Europe.
Within a single day, the world faced a rude awakening. Home-grown jihadist extremism in Europe is fully trained, locked and loaded. Andrew Parker, the head of our security services, has issued his most stark alert yet: that we are overdue a mass casualty attack in Britain. Such an attack is, as the government now warns, almost inevitable.
The reality of these attacks have moved government ministers to act, shocked journalists, alarmed the British public, scared Britain's Jews and disturbed British Muslims. As of now, the nation is collectively facing a grim truth: for whatever reason, and by whatever name, the various policies - or lack of them - adopted by governments across the continent to build socially cohesive communities have failed. To many, Britain's communities appear to be growing together, apart.
Record numbers of British-born Muslims have left their home country to join IS, the most brutal terrorist group of our lifetime. In fact, more foreign fighters have left than went to join al Qaeda in Afghanistan.
As Jihadi John has shown, British citizens are the worst of the theocratic fascists, rushing to Syria to slaughter freedom fighters, and everyone else.
Islamists can’t accept that Muslim and non-Muslim can live together
There are an estimated 500 to 2,000 British fighters in Iraq and Syria, with hundreds already returned to the UK. Such numbers do not emerge from a vacuum.
When surveyed, alarmingly high numbers of young, second generation Sunni Muslims express sympathy with IS's foundational idea: resurrecting a theocratic Caliphate and enforcing a version of Islam over society, aka Islamism.
Most qualify this by saying not in Britain, but somewhere, sometime, and soon. But it is not a great leap from wanting a Caliphate somewhere soon, to believing Iraq and Syria should be that somewhere now.
The widespread prevalence of Islamism among Europe's second-generation Muslims, and its institutionalisation in some cases, forms the toxic milieu from which jihadist terrorists are able to recruit.
Islamism cultivates the mindset that wherever Muslims are, they are but temporary residents of their countries, loyal only to the point of resurrecting a Caliphate. Once it is created, Muslim allegiance is said to be owed primarily to the Caliph. Until this happens, Islamists seek to work within Muslim communities to create the social, political and educational conditions for the Caliphate to emerge.
Islamists work towards this aim every single day. While they do, jihadists seek to bring about such conditions by force. Theirs is a difference of methodology, not ideology.
Alongside this, xenophobic, far-right and populist movements have emerged across Europe. These conflate an understandable rage against Islamism, with a barely disguised disdain for Muslims per se. It is no longer uncommon, even for long-standing counter-extremism activists like me, to be told that all Muslims should be killed or expelled from Europe. These far-right groups thrive off the divisions created by Islamist activity to prove that Muslims can never live in Europe as loyal citizens.
In selecting their target, the Paris jihadists made a tactical choice: Charlie Hebdo, a magazine renowned for satirising not only Islam, but all religions. The real strategic message the terrorists were sending to Europe's Muslims was an ideological one: you will never be able to live here, the "infidels" will never compromise, and nor can you, so the only solution is to separate, and form your own Caliphate which will "protect" your religion from such insults.
It is this narrative, of the impossibility of Muslim and non-Muslim cohabitation in Europe, that Islamists and far-right xenophobes agree upon. And it is this narrative that currently appears to be the loudest and most aggressive. Something has gone terribly wrong.
As the general election approaches, policy-makers will be rushing to appease a worried public by promising measures to address the homegrown threat. Alas, I fear it will all be more of the same. So far, we have been happy retreating to two unhelpful comfort zones. The first is one of stricter law and harsher war. The second is denial, a pretence that there's no problem, and a hope that it will all just go away because - of course - we mustn't be nasty to our helpless immigrant Muslims communities, especially if we want their votes.
But if it is true that we are facing an ideological problem, then no amount of law or war will address it, just as no amount of appeasement will deter Islamists from ideologically undermining our social cohesion. As the killing of Bin Laden proved, the problem has continued to metastasise.
What we as a society are woefully inadequate at, what we are simply not prepared nor equipped to face, is the long-term task of committing serious resources to uprooting the Islamist ideology in our midst.
Despite years of promise, there is still no official government strategy to challenge Islamism, just as there is no Europe-wide strategy to undermine the appeal of IS.
This would be neither a popular policy among Muslims, nor a cheap one, but it would certainly be an investment for a more cohesive and peaceful future.
Despite years of encouragement, many Muslim voices still remain reluctant to challenge Islamism within their communities, shirking all responsibility and preferring instead to focus exclusively on foreign policy.
Unfortunately, if this social division continues, the first victims of it all - after Jews who are attacked by both extremes - will be ordinary Muslims. It is not enough for us all to stand side by side in condemnation of violence.
It should go without saying that violence is wrong. What we are ignoring are the difficult conversations needed about what went wrong and why, which ideas lie at the root of this extremism, and how to challenge them.
All of us, Muslim and non-Muslim, are responsible for resisting the polarisation of our societies and are duty-bound to show one another solidarity in such resistance. All of us must be more active in challenging Islamist narratives, and in debunking the far-right tropes that thrive in their wake. Our integration policies are clearly inadequate.
We must articulate a new social contract for our new multi-ethnic societies, and we must start such conversations in earnest. The alternative is too bad to contemplate.
Maajid Nawaz is chairman of counter-extremism thinktank, Quilliam and Liberal Democrat parliamentary candidate, Hampstead and Kilburn
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