AS readers will know, this column has been playing a game of Project Fear bingo in the EU referendum, spotting the similarities with PF in the Scottish independence campaign. We’ve had: all will be poorer if we leave, check; currency instability, check; house prices will crash, check; terrorism could get worse, check; cancer research could be hit, check. However, as far as I can remember, no one actually forecast that Scotland leaving the UK would lead to a world war. Another Great Depression, yes, but not bloody conflict on a global scale.

Yet, that’s what David Cameron suggested might be the consequences of leaving the EU in his latest escalation of the Brexit war. His British Museum speech moved Project Fear to a new level. Blenheim, Trafalgar, Waterloo, Britain’s lone stand against Nazi Germany. “Rows of white headstones in gardens of remembrance” – this was high-octane stuff worthy of Stephen Spielberg.

It certainly riled the Brexiteers, many of whom have long suspected that the European Union is just German domination under another name. Similarly, some on the Tory backbenches fear the EU has achieved what Napoleon sought: a Europe united under the law and a common currency.

Clearly, Mr Cameron was trying to seize control of Britnat iconography before Boris Johnson got his hands on it. The former London Mayor is a bit of an historian and got his retaliation in within hours of the Prime Minister’s dawn raid. He said that, on the contrary, it is the policies of the EU that are the threat to peace and stability in Europe and that anyway it is Nato that secured peace, not the bureaucrats of Brussels.

It’s not at all clear how Mr Cameron thinks departure from Europe could cause another war.

But just for good measure he threw in Russian expansionism, Ukrainian separatism, Balkan nationalism, Islamic State among other threats.

He didn’t specifically namecheck Kim Jong-un , but no doubt the North Korean dictator is just waiting for the vote on June 23 before trying his luck.

Joking aside, Mr Cameron is partly right. The EU was originally about preventing war. In the 1950s, the architects of Europe like the French diplomat Jean Monnet regarded the EEC as it was then, not as simply an economic project, but a geopolitical one. It was designed to prevent France and Germany going to war by locking their economies together.

Nor was the single currency in 1990s just about boosting GDP. The late German Chancellor Helmut Kohl said in 1996 the euro was “a matter of war and peace in the 21st century”.

The theory, again, was that countries sharing a currency cannot go to war with each other.

However, that theory has never actually been tested, largely because war between Germany and France seems a remote possibility. Of course, a chaotic disintegration of the Eurozone could lead to conflict on the fringes of Europe. But Brexiteers say the tension is self-inflicted by the sovereign debt crisis and the EU’s failure to deal with refugees.

In a sense here, Mr Cameron wins both ways.

The common currency may have been a mistake, but no-one believes dismantling it now will be without risk. Britain is not in the Eurozone but if we left, others might follow our example. It’s a new version of the domino theory.

Greece would presumably be next. That could mean the return of the fascist right who dominated Greek politics for much of the last century.

Alternatively, Russia might intervene to help Greece and might then seek to use the disintegration of the EU as a pretext for pre-emptively “protecting” the large Russian populations in countries like Latvia and Lithuania.

The Balkans could easily be involved, and, of course, Ukraine.

Whether this could lead to full-scale war is another question.

My own view is that Mr Cameron is probably right about the chaotic consequences of Brexit at the moment when Europe is failing to cope with the twin problems of the refugee crisis and terrorism. That is the most credible case for remaining in the EU right now.

But it doesn’t help to overstate it. World War Three is not going to break out. The problem with Project Fear is that, as happened in Scotland, many people end up dismissing it as over the top and hysterical. And right now the polls are 50/50 on Brexit. When it comes to the EU the watchword should surely be: don’t mention the war.