So ends the honeymoon: the turmoil in Calais and its consequences in Kent have finally dragged David Cameron from the election winner’s podium down to political ground level and a harsh audit of his response to the cross-Channel crisis.

Labour, of course, is distracted to the point of irrelevance, squirming in a chrysalis that occasionally assumes the shape of a fossil. The most that the party’s interim leader, Harriet Harman, has mustered so far is a letter to Cameron, demanding that compensation be sought from France for those who have been inconvenienced. Hardly raises the pulse, does it?

The referendum will be a competition of warnings, a contest of threats rather than of dreams

Though you would not have guessed it in the days after 7 May, most of the right-of-centre media never really liked this prime minister, and spent much of the last parliament complaining about the concessions he had to make to his Lib Dem partners, the alleged inadequacy of his government’s spending cuts, and his supposed fixation with “faddish” causes such as same-sex marriage.

Cameron’s victory obliged what remains of the Tory press to put out the blue bunting and toast a politician they had been rubbishing for years as a man of destiny. The Calais fiasco has enabled them to revert to type and resume their routine attack upon the feeble Fauntleroy in No 10.

Since he became leader in 2005, it has always been Cameron’s intention to reframe the question of migration as a primarily administrative challenge, and to drain Tory discourse on population mobility of its poison, coded messages and dog-whistle innuendo. His policy has been driven by concerns about capacity rather than the cultural objections of the reactionary right.

In this context, his use of the word “swarm” to describe those seeking escape from north Africa was indeed, as the Refugee Council objected, “dehumanising”. But it was the exception that proved the rule, a slip at odds with his usual conduct. Whatever else Cameron is, he’s no racist.

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On the challenges posed by the forces of modernity – globalisation, development, migration – the government’s undisputed guru is Sir Paul Collier, professor of economics and public policy at Oxford. In his most recent book, Exodus: Immigration and Multiculturalism in the 21st Century,, Collier writes scathingly of “the political economy of panic” and dismisses the polarised opinions of both “xenophobes” and those who regard all migration limits as morally suspect.

As if using the book as his manual, Cameron does indeed lie dead-centre between these extreme positions: conscious that effective border control has become a basic test of governmental competence, but no less aware that a strong economy requires migrant labour and that a decent society does not turn away the afflicted, tortured or persecuted. Fortress Britain is a mad dream of those who hate only one thing more than modern Britain, which is the thought that anyone might want to come and live here.

The challenges encapsulated in the Calais drama will long outlast Cameron’s premiership. But there is an immediate and pressing reason for his personal supervision of the crisis – his chairmanship of a Cobra meeting last week – and for the anxieties coursing through the sinews of the government.

Much is written about the timing of the EU referendum and the growing preference for a date in 2016 rather than the year after. In fact, the criterion is unchanged: as soon as possible, but not until the political stars are aligned.

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Which they are not. The “in” campaign – which has just recruited Will Straw as its executive director – has many arguments on its side. What it conspicuously lacks is an idealism or sense of allegiance to which it may appeal. There is no European demos: to the extent that younger Britons acknowledge a supranational identity, it is global. The EU has been leapfrogged.

This means that the referendum will be a competition of warnings, a contest of threats rather than of dreams. The “ins” will say that leaving the EU would undermine Britain’s economic prosperity, its place in the world, even its relationship with the US. The “outs” will argue that this country has lost control over its destiny and must urgently wrench itself from the death grip of Brussels. And then they will say: just look at Calais.

At the heart of Cameron’s renegotiation strategy is the demand that EU nationals be eligible for tax credits, social housing or child benefit only after four years. Meanwhile, the immigration bill expected later this year will create an offence of illegal working and impose responsibilities upon hauliers to protect border security. In the short term, more sniffer dogs and fencing supplies are being sent to Calais. Ministry of Defence land is to be redeployed as a lorry park to ease traffic congestion in Dover.

None of this impresses those who long for Britain to leave the EU altogether. They counter that Cameron’s proposed benefit reforms will be offset by the new “national living wage”, a putative “migration magnet”.

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In an article for the Telegraph in June, the editorial board of the Eurosceptic campaign group Business for Britain argued that full control of migration could only be achieved by a complete break with European institutions. According to Matt Ridley, Matthew Elliott, Luke Johnson and others, the halfway house represented by membership of the European Economic Area would not release Britain from its obligation to respect free movement of EU citizens within the 28-nation bloc: “Exit from the EU and regaining complete policy freedom provides the widest possible choice. Taking a more global view is paramount.”

Elliott was the mastermind behind No to AV, the strategically brilliant campaign that saw off electoral reform at Westminster in the 2011 referendum. In those days, he and Cameron were on the same side. The prime minister knows he is an adversary to be respected.

Worse, the “outs” now have a showreel: news footage of young men running towards lorries and the Eurotunnel, trying to make it to England at any price. The proposition that Brexit would stop them in their tracks shows a heartbreaking lack of understanding of human nature, of hope or of desperation.

But in a world of competing images this one, you can be sure, will be abused again and again to make the case against continued EU membership. Like Mary Tudor, Cameron may yet find Calais engraved on his heart.