To understand why Britons will likely vote on June 23 to leave the European Union (EU), you have to go back to 1975, says EU expert Douglas Webber of the global graduate business school Insead.

The 61-year-old political scientist, who has long studied the politics and crises of the EU, told The Sunday Times this on a recent visit to Insead's Singapore campus.

On June 6, 1975, he noted, Britain's then Labour government held the country's first national referendum on whether the country should stay or leave the European Economic Community (EEC), the EU's precursor.

Sixty-seven per cent of British voters opted to stay, amid British press and business sentiment that was "overwhelmingly in favour of the EU", he said.

That, he added, was primarily because, in 1975, most Britons considered Europe "an anchor to save the British economy from drowning", as Britain was in such a bad shape economically that electricity had to be rationed and workdays cut short.

But now, the country's tabloids are "overwhelmingly hostile" towards regionalism. Last Monday, for example, The Sun - Britain's biggest-selling newspaper - had on its front page the headline: "BeLeave In Britain". It was a reference to the anti-EU Leave camp, as opposed to the pro-EU Remain.

Britons in business, Professor Webber noted, were now also "far less monolithic" in their attitude towards EU membership than they were 40 years ago, when they were "overwhelmingly" for integration with Europe.

Add to that the fact that Britain's Conservative Party is split on Brexit - with Prime Minister David Cameron for, and his political nemeses Boris Johnson and Michael Gove against it - and the upshot is that there is far less Tory muscle to mobilise the masses either way.

Britain's Labour Party, meanwhile, had warmed to the idea of EU in the past 25 years, with Labour stalwart Peter Mandelson among the EU's loudest champions.

But, said Prof Webber, "they don't want to do David Cameron any favours by bringing about a vote to stay in".

For these reasons, he thought there was a "real likelihood" from the outset that Britons would vote to leave the EU, but now thought the vote would be "very, very close".

Immigration was the last card the Leave camp had to play, he said.

He noted that total net migration to Britain last year was, at 333,000 people, the second highest in the country's history since 1975.

Of these, 149,000 were from places such as India, Pakistan, Australia and New Zealand while the remaining 184,000 were from poorer East European states, such as Poland.

The intense and careful don is himself a migrant from New Zealand, who got his PhD in Government at Britain's University of Essex in 1980 before teaching at various British universities. In 1991, he joined Insead at its headquarters in Fontainebleau, France.

The thing was, he added, official British government data showed that EU citizens working in Britain were net financial contributors to the British economy. "So," he stressed, "I don't think you can make creditably the argument that these migrants are a strain on British taxpayers."

Even so, last Thursday, hours before pro-EU Labour MP Jo Cox died after being shot and stabbed in her constituency, the xenophobic politician Nigel Farage unveiled Nazi-like posters showing a vast queue of non-Caucasian migrants with the words "Breaking Point".

He and others in the Leave camp mainly argue that the EU is authoritarian and dilutes British-style democracy.

But Prof Webber disagreed. He noted that EU members decide by consensus at least 80 per cent of the time: "It's quite rare for Britain to be outvoted in Brussels… It may have become a tendency for Britain to be out-voted more than any other member state in the past five years or so, but on a relatively small number of rules and regulations."

He was, however, not swayed by the large Remain camp's chant that EU member states are so economically interdependent that Brexit would not be worth the ensuing economic fallouts.

He said such interdependence is "far more fragile" now because the very forces that drove and continue to shape integration in Europe - namely the moderate Christian Democrats, liberals and Social Democrats - are now being supplanted by the "nationalist, xenophobic and anti-Europe" politics of France's National Front, Germany's The Alternative for Germany, Spain's Podemos and Greece's Syriza.

Also, the EU's two biggest powers besides Britain, namely France and Germany, are strained economically and politically. For instance, France's unemployment rate is 10.2 per cent - compared to 4.3 per cent in Germany - and its National Front's Marine Le Pen, for one, is through to the second round of presidential elections next year.

That leaves Germany to "keep the EU on the rails", an effort which he said is being "curtailed" by its growing pool of extreme right-wing politicians.

All told, he said the EU could shatter forever in two ways: First, if there was "a complete collapse of cooperation between member states", and second, if the Middle East completely collapsed, sending a further flood of refugees into Europe.

"Sometimes," he mused, "Europe is described as being encircled by a ring of fire. And that's not too far from the truth."

Correction note: This story has been updated for clarity.