Sketch: My Muslim brothers! Join the Bent Banana jihad! Isis comes out for Brexit

As David Cameron claims Isis leader Abu Bakr Al-Baghdadi backs Brexit, at least the referendum opinion co-opting has moved on from the dead to the living

David Cameron addresses members of a World Economic Forum event focusing on Britain's EU referendum in London (AP)

The Prime Minister must have panicked. It was a tough crowd, after all. A room full of businessmen in the heart of the City of London. Mansion House no less, the very room where he comes once a year wearing white tie to eat the Lord Mayor's fillet steak.

“It is worth asking the question who would be happy if we left?” Cameron said. “I suspect al-Baghdadi might be happy.”

You could see it in his eyes, he knew he’d cocked up straight away. Like when he forgot what football team he supports, only this was worse. He knows there’s still five weeks to go and he wasn’t meant to do the Isis thing until June at the earliest, or until everyone’s bored with Hitler, whichever is soonest.

It’s possible it worked though. The Isis social media team are furious. Vote Leave are threatening to sue. Al-Baghdadi himself has been been forced into rushing out his latest propaganda video weeks ahead of time. You can watch it on youtube now.

“My Muslim brothers, join the Holy War for the prawn cocktail crisp!” you can hear him shout, as he rides a tank up and down the side of a giant EU butter mountain in the desert. “As mighty Allah told the Prophet Muhammad, ‘Do not eat the infidel's straight banana!"

The crackle of unregulated Kalashnikovs rises in the background, as jihadi fighters burn copies of the EU working time directive.

“Death, my Muslim Brothers! Death to the European Court of Human Rights, which bans the throwing of gays from the tops of buildings! In the name of Allah, avenge the transferral of national sovereignty to Brussels!”

All this will have taken many of the Brussels crowd by surprise. After Ukraine and Turkey were sorted out, it had been hoped to that the Islamic State might be persuaded to join the European Union themselves. It is already an enthusiastic member of Schengen after all.

Still, as far as the Brexit debate goes, it’s a clear improvement. Isis, it cannot be disputed, is still alive. It’s possible this intervention might mark the point at which the debate moves into the more enlightened territory of co-opting the opinions of the living, rather than the dead. Having already had both sides argue the toss over Churchill, Thatcher, Emmeline Pankhurst and everyone else up to and including former Aphrodite's Child front man Demis Roussos, at least Isis, Trump and Putin are around to agree or disagree.

If Isis definitely can’t be persuaded, Cameron wisely honed in on those who have yet to make up their minds. As the Vote Leave crowd bear down on what Boris Johnson likes to describe as the “Davos men and women who have their jaws firmly clamped around the euro-teat,” here was the Prime Minister, assembling a satellite state of Davos in the middle of the City of London. This was a ‘World Economic Forum’ event. A Swiss man called Yann who's a very big deal on LinkedIn was on hand to dish out the lanyards. When it comes to preaching to the converted, this was right up there with Al-Baghdadi’s Friday sermons in Raqqa.

“Why doesn’t the electorate respect the EU in the way it should?” One man asked in the Q and A at the end. Ah, the infidel. There are ways to persuade them.