By Sadiq Khan, Labour's candidate for London Mayor.
It could have been us. That’s what everyone in Britain has been thinking since the horrific attacks in Paris last week - and they’re right. It could so easily have been the bars, restaurants and concert halls of London, Manchester or Glasgow.
Earlier this year, my wife and I took our two teenage daughters for a short break in Paris.
We had a great time - eating in restaurants just like those that were attacked. We even went to a gig - in our case to see The Kooks - enjoying a night out just as those at the Bataclan had planned.
This wasn’t just an attack on Paris, it was an attack on our shared way of life. They were horrendous crimes committed by sick and evil people - in the name of a sick and evil ideology.
And when you see the polling in The Sun today, It’s clear that Britain needs to take its head out of the sand - and act to tackle extremism and radicalisation at home.
Tackling extremism is a challenge for everyone in Britain - but I believe that British Muslims have a special role to play.
Why? Not because ordinary Muslims are responsible for the evil extremists who pervert their religion – the real Islam is peaceful and tolerant.
But because Muslims are best placed to ensure the extremists messages of hate and death are not believed by other Muslims.
British Muslims must challenge these extremist views wherever they come across them.
They must absolutely insist that British values and Muslim values are one and the same, and give the next generation of Muslim leaders the confidence they need to say this loudly and clearly.
The fight against extremism is personal for me. As The Sun's polling shows today, the reality is that most British Muslims have come across someone with extremist views - and I’m no different. It has affected my personal life, my friendships, and my career.
I worry about the safety of my daughters. Could they, or their friends, be groomed by extremists on the internet, or even tricked into running off to join ISIS - as other British kids already have? How could any family cope with that?
People I knew as a boy have gone on to hold extremist views and, as a lawyer, as well as representing people who were badly treated by their bosses, I occasionally had the deeply unpleasant job of representing people with extremist views.
It was horrible - but it went with the job.
Every time I’ve stood for Parliament, I’ve been subjected to a campaign of hate from the extremists. They gave out leaflets in my community, telling people I’ve known since I was a boy that I’m destined to go to hell.
They tried to tell my friends and neighbours that voting is banned in Islam. They said that that Muslims shouldn’t take part in democracy - that we shouldn’t be the ones helping to put together man-made laws.
All this has been incredibly hard for my young family. Who wants to have to discuss police protection advice with their daughters? I don’t want anyone else to have to go through what I’ve experienced because of these people.
So It’s time we got serious about tackling the social segregation in Britain, which creates the underlying conditions that allow radicalisation to thrive.
For decades, successive governments have allowed Britain to become an increasingly segregated society. Too many British Muslims grow up without knowing anyone from a different background. And too many British people have never befriended a Muslim.
They’ve never worked together, eaten together or played sports together. As a result, too many people have formed a single identity based around their religion or ethnicity – rather than a shared British identity.
That means there is less understanding or empathy with the lives and beliefs of others. As we have seen, this can help give rise to Islamophobic hate crimes here in Britain, which must be roundly condemned.
Ending segregation will take a prolonged and concerted effort by us all. As Mayor of London, if I win the election next May, I’ll work with the Football Association, the England and Wales Cricket Board and others to set up community sports leagues bringing together kids from different faiths and different backgrounds.
This would help build on the example already provided by Muslim role models in sport, such as Mo Farah and Amir Khan.
And I’ll promote organisations which encourage people from different backgrounds to get to know each other at all ages – like the brilliant Big Iftaar and Mitzvah Day initiatives which are run by the Muslim and Jewish faiths respectively.
Moreover, ahead of Chancellor George Osborne's Autumn Statement this week, I’m deeply concerned that the Government is making decisions that will make it much harder for us to tackle extremism. Particularly the massive cuts to policing that have been proposed.
The Metropolitan Police Commissioner, Sir Bernard Hogan-Howe, has warned that further cuts to neighbourhood policing will make it much harder to get the absolutely vital intelligence we need to stop extremism.
Stopping terrorism increasingly relies on community information, and less on the intelligence service. The hollowing out of neighbourhood policing puts this intelligence gathering work at risk. It's a price we simply can't afford to pay.
I’m deeply worried that ministers haven’t done enough to ensure that children can’t access extremist materials on the internet. Most radicalisation doesn't happen from sermons in Mosques - it happens in the unguarded spaces of the internet. I’ll work with the Government to force the internet providers to get their act together.
It’s really important that we overhaul the Government’s de-radicalisation programmes, such as 'Prevent’. Decent, law-abiding people view these programmes as counter-productive. They are clearly failing - we still see more and more young people becoming radicalised.
Of course, The vast majority of Muslims in Britain are among the proudest, most patriotic and most hardworking members of our society.
They are industrious and full of the entrepreneurial spirit – contributing massively to our economy. They are charitable and compassionate.
And they want us to tackle the extremists more than anyone else - as the Muslim of council of Britain showed with its newspaper advertisements condemning the Paris attacks "unreservedly".
That’s why I decided to speak out and to ask British Muslims to do the same. We can't go on any longer thinking that this problem will solve itself. It won't. We must act to challenge the extremists and make Britain a properly integrated society once and for all.