A silly question was asked and a silly answer was given. That is democracy. But so is leadership. As the good ship Tory government smashes on to rocks of its own devising, David Cameron cannot desert the bridge. He has made a massive misjudgment, but it was one in which almost the entire British establishment has colluded.

They must all now perform a U-turn. They must behave as if Project Fear was overstated. Every muscle must be strained for a new relationship with Europe. Other leaders of the EU, fearing similar disintegrating pressures, must know they all have a vested interest in minimising the damage. The idea of “punishing” Britain will merely compound the stupidity and risk to European stability.

The immediate job is not to reflect on causes but to get down to work. The referendum is consultative. Procedures must be followed. For the time being, Britain remains a member of the European Union, but parliament must honour the government’s commitment to the British people to adhere to their decision. Officially that takes two years, though in Europe anything can happen. The French government in 2005 contrived to disregard a popular rejection of the Lisbon treaty.

As some advocates of leave claimed, leave can mean many things. No one has an interest in exaggerating the harm. Britain will have to reach a deal, on trade and other things, that will be novel and peculiar whatever the cost. It is Cameron’s parting duty to negotiate it. No one can have the slightest interest in his past threats of closed borders, collapsing trade and punishment budgets. The slate is wiped clean.

The biggest threat from this referendum is, in truth, not to Britain but to the rest of Europe, which is why the EU should think carefully about how to respond. It has been judged by this referendum and found wanting. Britain will not be the last to tell it so. Polls have shown between a quarter and third of people across Europe are now deeply hostile to the European project. The economies of southern Europe are in a Germany-induced lockdown. Brussels, and its German paymasters, are in trouble.

Britain should have been party to helping Europe out of this trouble. It should now take the initiative and be party to helping from the outside. The visionary outcome of a leave vote ought to be a grand debate across the continent, a search for a new confederacy of nation states. What is needed is a new Europe for the 21st century, to replace the ramshackle corporatism erected in response to the 1945 settlement, a confederacy in which Britain should be proud to participate. That vision may yet be far off, but so once was the EU.

As for Britain, it has given itself an almighty shock. Scotland may well be impelled to even faster independence, whatever that may mean in the context of whatever is negotiated with the EU. A bigger casualty has been London, which voted overwhelmingly for remain. It is revealed as a city statelet out of touch with its hinterland. Its morale and even its wealth have taken a severe knock, which to many outsiders will be no bad thing.

A half-century of metropolitan arrogance and centralism, to which all governments and all cultural institutions have subscribed, has gone suddenly rotten. Future British governments can no longer pretend at devolution. The capital has grown too big, too fat and too rich. Brexit will take it down a peg – or three.

How this is to happen is this morning impossible to envisage. Cameron and his amanuensis, George Osborne, clearly did not expect their gamble to fail. Cameron should have copied Harold Wilson in 1975 and stayed above the fray, guiding his country through a decision he asked it to decide for him. He is now the agent of a popular decision which he is charged with honouring. But the onus is on his leave colleagues now to prove their case, that leave would not harm Britain but benefit it. They may be cock-a-hoop, but it is they who are now on trial. If Boris Johnson and Michael Gove are really to be in some reconstructed government, they deserve to feel the heat.