I set up the Muslim-led fund for the victims of the Westminster attack – this is what I want to say to my fellow Londoners

“This can't be real”. Those are the words I heard over and over as I and several MPs and staff looked out of the window at Portcullis House and saw a car slam into the railings. Someone mentioned Jo Cox. Someone else – a Muslim – muttered a prayer for safety.

In the last year I’ve worked in Israel, Turkey, and Saudi Arabia – but only in London have I felt sheer terror.

It was only later, hearing the words coming out of my mouth whilst being interviewed for the News at Ten, that I realised that Wednesday is a day that neither I nor my city will ever forget.

I’m embarrassed to admit that my shock is turning into anger. Embarrassed because anger is the last thing we need – it’s anger, one man’s anger, that has got us here in the first place.

I’m angry at the perpetrator. I’m angry at myself for being so helpless. And I’m angry that all my fellow Muslims can do is condemn the attack. Isn’t there more? And do I really need to remind my fellow Londoners, my fellow Brits, my fellow human beings, that the only jihad fought that day was by the ambulance crews? That the only martyrs are PC Keith Palmer and four pedestrians?

And most of all, I’m angry that I don’t know what we do next. A vigil? A hashtag? A meme? I’ve started a campaign to raise money for the victims, Muslims United for London, joining forces with friends, and two British Muslim MPs, Naz Shah and Yasmin Qureshi. But what else?

I’m a professional communicator, but I’m lost for words. What was this? Simply calling it an “attack” seems too remote, too clinical. And what kind of attack? I don’t want to give Isis credit, but we must face the fact that the attack was likely inspired by their ideology.

But what is “Islamist” about this? Islamism – political Islam – is usually about banning alcohol or imposing the hijab. Mowing down schoolchildren from Brittany and a mum on her way to pick up her kids isn’t Islam or Islamism or any other –ism. It’s murder. Deranged, soulless murder.

The perpetrator, who I choose not to name, according to reports seems to have converted to Islam in prison, after a criminal career going back to the age of 18. His story is typical: a longstanding disregard for the rule of law and the rights of others being given a religious veneer after the fact. His violent nature was a pre-existing condition. This is the Islamisation of criminality. The absurd fact is, if Imams carried out CRB checks before accepting Muslim converts many terrorist attacks would be averted – we'd just call them murders instead, or maybe “GBH attacks” (for which the perpetrator had a prior conviction).

Yet we cannot deny that soulless murder is being justified in the name of Islam. A lot has been said about the UK’s Prevent strategy, especially amongst my Muslim friends. Many of them have joked about it being the “Agitate” strategy, perhaps oblivious to the fact that a quarter of Prevent reports relate not to Muslims, but to far-right groups. Prevent may mean you worry about your nephew’s tweets, but it may also stop him being stabbed in his mosque.

At least that’s the idea. What we now know is that the current strategy hasn’t prevented this. It has often cast the net of suspicion so wide that it alienates perfectly loyal Brits while letting real extremists slip through. But the attack outside Parliament shows that the need for a strategy to prevent Britons engaging in acts of mindless killing has never been greater.

Prevent is being reviewed and relaunched. The temptation to resist and reject, given past failures, is understandable – but it is not workable. We British Muslims need to be part of the new strategy.

Prevent 2.0 needs to be more ambitious, but also more nuanced than our previous attempts. And it must be more than a rebranding exercise. It must work in and with our communities to enable them to build resilience against those who would divide us.

The wall that Prevent has hit in the past requires both government and communities to make renewed efforts to speak to each other and create new ways to work together: because we all suffer when extremists strike.

To succeed, we will continue to need police and security services, but we will also need social workers – and psychiatrists. Because, as I was told at the UN last year, wars begin in the minds of men, and it is in the minds of men that the defences of peace must be constructed.

This can be real. It has already been real in Tel Aviv, Brussels, Berlin, Paris, Nice and Dewsbury. It has been real in Baghdad, Istanbul, Dhaka, Tripoli, Tunis, Sanaa, Cairo, Beirut, and beyond. Now it is real in London.

Either we live together – or we die together. That is real.