The migrant crisis in Northern France is getting worse by the day. It is said that up to 10,000 would-be migrants are presently camped in the holding centre known as the “Jungle”. Some of them have turned violent, threatening lorry drivers and motorists on their way to the Channel ports. Others – maybe the same ones – have been harrassing the locals, raising tensions to levels not seen since the Occupation, or perhaps since Edward III laid siege to Calais in 1346.

A majority of the Jungle dwellers are not genuine refugees. There are, it is true, a substantial number from Eritrea, mainly Christians fleeing that country’s deeply unpleasant Islamist dictatorship. There are also Afghans, Iraqis, even Syrians, whose experiences should command our sympathy. But the majority – two-thirds of them male – are Sub-Saharan Africans, who simply want to be be given homes, jobs and benefits by the English (i.e. not the Scots) and are not prepared to take no for an answer.

For the good burghers of Calais, and other parts of the Channel coast, the situation has turned into a nightmare from which, apparently, they cannot expect to awaken anytime soon. Until the problem arose, just before the turn of the millennium, the chief business of Calais was the comings and goings of the Brits, who not only entered and exited France via its port and the nearby Eurotunnel, but also regarded the town as somewhere they could stuff mussels and chips down their necks in-between loading up their cars with cheap liquor.

No one, including the French, loves the Pas-de-Calais, but it was familiar territory, dripping with shared history – the Field of the Cloth of Gold; the Siege, the eventual re-capture by France that caused Queen Mary to claim that when she died they would find “Calais” (or “callous”) engraved on her heart; the BEF’s evacuation from Dunkirk in 1940, with all its heroics; and, finally, the booze cruises of the 1980s, complete with projectile vomiting and requests that the French should speak English.

All changed, changed utterly. Now Calais, so far as the English are concerned, has become a grim gauntlet which they have to run if they are to make it onto their ferry or shuttle in one piece, without stowaways.

Life goes on, of course. The port continues to function. Each year, 6 million passengers, 2.1 million lorries, 2.8 million cars and motorcycles and 86,000 coaches pass through Calais and Dunkirk on their way to and from Dover. Annually, another 2.6 million cars arrive at Calais Fréthun, the Eurotunnel terminal, plus some 1.5 million trucks laden with 19.3 million tonnes of freight.

It isn’t big business, it’s huge. If it didn’t exist, we would have to invent it.

But, after a recent spike in violence – the French have had enough of migrants turning their money-spinner into a pit of despair. More to the point, the people of the Pas-de-Calais have had enough. They have stood by as scores of their restaurants emptied and closed. They have watched their booze warehouses turn into white elephants. They have looked on, aghast, as their bars are boarded up for lack of business. They worry about walking the streets after dark, or even in the daytime. They keep their doors locked and their shutters closed. In short, they are sick to the back teeth of the second siege. If they don’t get action, they are threatening to take matters into their own hands.

Back in 1346, Edward III, buoyed up by his recent victory at the Battle of Crécy, demanded some show of humility and sacrifice on the part of Calais as an incentive to him not to sack the town. But when six local dignatories offered themselves to be executed, the king was persuaded by his wife to spare their lives, which he did.

Today, Calais feels that it has already made sacrifice enough and is demanding that Britain lift the siege.

Which is where we run into difficulties.

Under the grandly named Treaty of Le Touquet, signed in 2003, France agreed to establish immigration controls at the ports of Calais and Dunkirk to ensure that passengers on their way to the UK had valid passports and, where appropriate, visas. Mirror arrangements were put in place in Dover, though without the same sense of urgency, since few Brits and others actively seek to smuggle themselves into France.

Under French law up to that point, ferry and train operators had no responsibility for checking passengers’ papers, other than their tickets. Indeed, it was an offence for commercial undertakings to usurp the authority of the immigration service. At the same time, uniformed douaniers and police rarely bothered to do more than wave people through – leading to the arrest of thousands of illegals each year on the UK side of the Channel.

The Touquet deal (I know, dropping the “le” looks odd) established a new, one-off protocol whereby not only did the French smarten up their act, but British immigration officials and Kentish bobbies were stationed in France to double-down on those who sought to gain unapproved entry into Her Majesty’s realm. Over the years, as the numbers of Third World migrants mushroomed, all of them intent on reaching the promised land, the thin blue line was reinforced with concrete and steel, so much so that today the approaches to Calais are like one of those authorised approaches into the old East Germany from the West described by the travel writer Jan Morris as “like entering a drab and disturbing dream, peopled by all the ogres of totalitarianism, a half-lit world of shabby resentments, where anything could be done to you”.

Britain’s Home Secretary Amber Rudd travelled to Paris yesterday (by what means I know not) for talks on the crisis with her French opposite number Bernard Cazeneuve. France’s Socialist Government has up to now been uncharacteristically reasonable on the subject, riding roughshod over the mayor of Calais and the region’s conservative president Xavier Bertrand. Cazeneuve, however, is a tough cookie, with considerable reserves of political ambition, and his nose will be telling him that the time has come to talk tough.

The two leading candidates from the Right vying to secure their party’s nomination for the presidency have spoken out strongly on the issue in recent days. Nicolas Sarkozy used a bully pulpit set up in Le Touquet itself to rail against the British, insisting that, post-Brexit, they must take control of their own borders and process migration and asylum claims in Dover, not Calais. Alain Juppé, a former prime minister and current favourite for the nomination, was, if anything, even more forthright, while their Républicain colleague, Bertrand, having suggested a full-scale UK immigration “hot-spot” in Calais, aimed at emptying the Jungle (an idea Britain has rejected as a “non-starter”) has since said it is time to abandon Le Touquet and, unlike Theresa May, embrace the nuclear option. Needless to say, Marine Le Pen, the Front National leader takes the same view, but with knobs on.

Critics of both the French and the present arrangements have pointed out that a reversion to the status quo ante is all that is needed – in other words, a simple procedure under which no one gets to board a train or ferry who doesn’t have the relevant documentation. They argue that the ferry companies and train operators can easily manage such a system, while hinting loudly that if they don’t they should face enormous fines.

All well and good. But who would police any such arrangement? Who is to say that the French in this scenario will not revert to type, waving passengers through and leaving cars and lorries largely unchecked? Would it then be down to the ships’ crews, half of whom are French (or Polish)? If the presence of hundreds of UK immigration officers and police confers little by way of added value, then why is the Government arguing so strenuously that they must be allowed to remain? What happens to the complex of physical barriers erected at UK expense, requiring regular maintenance and apparently endless extension? And, most importantly, what happens when the residents of the camps in and around Calais perceive that the French, including the CRS, have switched sides and that, with a little enterprise, their dreams may yet come true?

Don’t worry, the apologists say. France needs a functioning Calais as much as we do. That’s true. But never underestimate the bloody-mindedness of the French when they feel they are being taken for a ride. Don’t imagine either that with Brexit round the corner after next, Paris isn’t ready to push the reset button.

It is all a hideous mess. Blame can be apportioned in every direction. But either the two governments come to an arrangement under which Britain takes some measure of responsibility for the steady stream of humanity heading in its direction, or else, as far as the French are concerned, the problem will have to be moved on – that is, to Dover. It is not enough for Britain to claim that it is not their problem – that they didn’t invite these people. The fact is, the UK boasts of its open economy and, according to official estimates, employs hundreds of thousands of illegal workers. Nor will it do for ministers and other apologists to point out that the migrant build-up in France should never have been allowed to happen in the first place. That is all water under the bridge. You might as well say that the British Border Force should have a fleet of seaborne patrol craft. They don’t. (They have three elderly cutters in home waters; the fourth is in dry dock to save money.)

The migrants exist and their numbers are growing. Many of them have thrown away their passports and cannot readily be repatriated. Calais, meanwhile, is being turned into a ghost town. France wants action, and if it doesn’t get it, it will almost certainly take unilateral action next year. Be warned: the Garden of England may yet have to incorporate a jungle.