The EU has an impressive past. In 1945, Europe was ravaged. It was not clear whether the countries which became the EU’s founder-members would ever recover. ‘Europe’ under its various acronyms helped them to attain prosperity and relative political stability. It assisted Spain and Portugal to achieve democracy and modernisation. At Yalta, the Allies had to abandon half the continent. When the Soviet Empire collapsed, the EU was waiting to welcome the escapees from oppression and Comecon. At that point, it could have claimed to be as successful as any multi-national organisation in history. Then everything went wrong.

This was largely due to a tragic misreading of history. In 1945, many Europeans believed that the age of the nation state was over. Its wars had almost destroyed Europe, so nations had to be superseded. But that was an error. In some unfathomable fashion – a version, perhaps, of Hegel’s ‘List der Vernunft’ – nations and individuals can learn from history and can change in response to the lessons. Thus it was after 1945 in Europe. Aggressive nationalism left the agenda. But nations need nationalism, not to inspire them to invade their neighbours, but in order to feel that their laws and liberties are protected by people who have emerged from their political system: in order to feel at home. Families need homes, as do countries. Once Europe recovered, so did its nation-states. This did not mean that France and Germany were about to go to war over Alsace-Lorraine.

But Helmut Kohl was still stuck in 1945. He was determined to unite Europe before the war-guilt/war-scarred generation passed from the scene. The single currency was his chosen instrument: a disastrous one. Single currencies cause difficulties even in single countries. Mayfair and Manchester, Manhattan and Mississippi: it is not always easy for such divergent local economies to have the same interest rate. The problems can be managed because there is a common language plus – to an extent – free movement of labour and – also to an extent – a unifying patriotism. Above all, there are fiscal transfers. So a single currency is underpinned by a single fiscal policy and by a single polity.

Little of that is true in Europe. Herr Kohl was building the roof before he had laid the foundations. The results: economic sclerosis, large-scale youth unemployment, political alienation – and there is no obvious solution. Those of us who predicted the early demise of the Euro have worn out several sandwich-boards; there is a lot of ruin in a single currency. But it cannot work without political union; how likely is that? So it would seem that as the Euro can neither go forward nor backwards nor stay the same, its subject members are trapped until there is an implosion, probably caused by riots in France.

The EU has an impressive past, and a future wreathed in dark clouds. To many Tories, never enamoured of the European project, that would seem to be a strong argument for leaving. On the contrary: it is a conclusive argument for staying. Britain must remain a member, in order to help clear up the mess.

Tories should never be afraid of paradoxes, like that wonderful Irishism: ‘Well, this pig does not weigh as much as I thought it did, but then again, I never thought it would.’ Complex events are best approached in a spirit of tough-minded eupeptic pessimism, for Tories also know that there are no magic wands. Europe is an unspeakably complex event, and there is only one point on which we can be certain. There is no alternative to engagement with the continent. Even though his Britain was a world power and an Imperial power, Churchill probably spent as much time thinking about Europe as any Twentieth-Century statesman, and an implicit conclusion emerges from everything he wrote, said or did. We have to be involved. We do not accept everything the EU stands for: no Schengen, no Euro, no ever-closer union. But we must find a modus vivendi.

If we left, no-one would have the least idea what new relationship would emerge, if any. For months running into years, there would be trouble and uncertainty. Confidence would suffer – and forget any talk of an amicable divorce. The others would be thrust into prolonged and, no doubt, ill-tempered negotiations. France and Germany have elections on the horizon. Lots of other countries have domestic strains and stresses. There would be widespread incomprehension and, indeed, widespread anger. Plenty of people on the continent would want to punish us. Above all, they would fail to see why we, who have spurned them, should continue to earn many billions a year by handling such a large percentage of their financial transactions. Would they succeed in cutting us off? No-one can tell. But plenty of the biggest City institutions are worried as are most big manufacturers.

Moreover, if Brexit were in Britain’s interests, it would also be in other countries’ interests. So how many third countries are encouraging us to leave? Answer, one: Mr Putin’s Russia. Donald Trump is also a Brexiteer. Does that fill anyone with confidence? All the major international financial authorities, all the central bankers, all the major financial centres – have all come to the same conclusion. The Brits would be crazy to leave. Can every one of them be wrong?

We live in unstable times. Over the next few months, what will happen in Russia, the Middle East, China? Even if the answer turns out to be ‘nothing much’, neither the question nor the uncertainty will go away. What is going to happen in American politics? One thing is clear. There will be no great pressure from Washington for more free trade.

As for the UK, we have a strong but fragile economy. We are growing, but the hope that we would move strongly ahead post-recession has not been realised. The annual deficit is still alarmingly high and taxes are burdensome. We need several years of steady growth; we cannot afford to slide back into recession. But if Brexit prevailed, that would be all too likely. Even many Brexiteers have admitted that there would be short-term economic damage and when economies turn down, short terms can easily lengthen. Britain faces a number of problems. None of them would be alleviated by Brexit; many would be exacerbated.

If Remain should win, there would be a sigh of relief throughout the chanceries of Europe – but not a sigh of complacency. For years, although the EU has been talking about reform, little has happened. We would have brought the issue up the agenda. Prime Minister Cameron would insist that it would stay there. Britain would not have given Europe a blank cheque: merely a last chance.

Geopolitics and global economics are both beset by unpredictability. This is the era of the unknown unknown.

So this is no time for gratuitous risk-taking. Brexit would be a leap in the dark.