No Prime Minister has made a bigger miscalculation since Eden

So, farewell then, David Cameron. No Prime Minister has made a bigger miscalculation since Anthony Eden thought he could get away with invading Egypt in 1956 to recapture the Suez Canal. Going for a referendum on the country’s geopolitical state as if it was a council regulation on dog-fouling was a very big mistake.

The attractions must have seemed obvious at the time he made the promise, not the least of them being a hope that it might buy off divisions within his party and prevent defections to Ukip. But instead of lessening divisions, it has deepened them. His successor will have their work cut out trying to heal the party.

In his dignified resignation speech, David Cameron told us that “the will of the British people is an instruction that must be delivered.” How this mess is to be cleared up is the first question.

For nearly 50 years Europe has been the main project of the Foreign Office: any ambitious diplomat wanted to serve there. Hence Norman Tebbit’s quip that “The job of the Ministry of Agriculture is to look after farmers. The job of the Foreign Office is to look after foreigners.” It went far deeper than that, of course. The European Union had entered the bloodstream of the British public service, and there was not a department in Whitehall that did not have an eye on Brussels.

So the first problem is to reboot the official mindset. Britain has not negotiated a bilateral trade agreement for 40 years. Perhaps there are some retired civil servants who can be winkled out of their vegetable plots to give advice. As they shake the soil from their corduroy trousers, they had better also contemplate the depths of small-mindedness they are likely to encounter when trying to haggle with a slighted European Union desperate to discourage other nations from following Britain through the exit.

Appearing among the largely unrecognisable middle-aged men and women in the so-called “family photo” at the end of every European gathering has become the dream of politicians across the Continent.

But becoming part of that club is a dangerous thing. “Jaw-jaw is better than war-war,” Churchill is supposed to have said at a White House lunch.

The problem is that politics requires politicians, and politicians must have things to do. The building of a United Europe has been their project for decades. In the process, too many seem to have forgotten the people for whom they were building it.

So during the referendum campaign party leaders, Cabinet ministers, ambassadors, financiers, tycoons, the Governor of the Bank of England and even Barack Obama all said the same thing. And in the end, the voters gave them an enormous raspberry. People do not like being lectured. But they do rather like a promise.

At no point did the Remain camp paint a visionary picture of why a United Europe is desirable to set against the sub-Victorian trading dreams of the Leave campaign. A mature approach would have been to admit: “Yes, it’s inefficient and not properly democratic, but the soil of Europe is soaked with blood and it’s surely better that we talk and trade than that we shout and fight?”

The most passionate advocate of membership turned out to be the actress Sheila Hancock during a debate we staged on Channel Four the night before the vote: she wanted to remain inside the European Union for the sake of her grandchildren and for peace. By then there were only nine hours until the polls opened and it was much too late.

That evening’s bear-pit was notable for something else. The various politicians present – the people we elect in representative democracies to make these decisions for us – were notable by their modest silence. Yet