When a majority of the British people voted to leave the EU in 2016, I was struck by the similarity between the Brexiteers’ plans for their perilous voyage and those of Edward Lear’s characters in The Jumblies as they set to sea in their sieve. The analogy became more apt as the proponents of Brexit showed that they did not know nor care very much about the nature of the world into which they were proposing to sail other than to hope that everything would be alright on the night.

The Jumblies, like the Brexiteers, were swift to dismiss critical comment predicting a disastrous end to their venture, saying: “Our sieve ain’t big / But we don’t care a button, we don’t care a fig! / In a sieve we’ll go to sea!”

The water did indeed come in, but the Jumblies were not downhearted “because they wrapped their feet / in pinky paper all folded neat”. For extra safety, they pass the night in a crockery jar where they sang of their wisdom as they set their pea-green sail for lands where, among other things, they secured an owl, a pig and some green-Jack-daws, and “a lovely monkey with lollipop paws”.

The Brexiteers’ alternative to the EU is just as imaginary as that described by Lear as a habitation for the Jumblies. The reason why the Leavers have failed to negotiate the sort of settlement they said they wanted from the EU is simple: what they said in 2016 was based on the proposition that the EU got more out Britain than Britain got out of the EU. Had this been true, the British departure would be easy enough, because Britain could genuinely have threatened to walk away. But because Britain needs the EU more than vice versa, the outcome of the negotiations were always going to be heavily skewed in favour of Brussels.

Yet this simple proposition evidently eluded Dominic Raab, David Davis, Boris Johnson and the other Leavers who departed from the cabinet claiming that Britain was being blackmailed and bullied into submission. Successful negotiations always reflect the balance of power between the negotiating parties and it is puerile to believe that the settlement, which the EU leaders will or will not agree to in the next few days, was determined by a failure of will by Theresa May or subtle treachery by Remain-sympathising civil servants.

It is easy and right to deride the Leavers for their wishful thinking and inability to calculate the true balance of power between Britain and its neighbours. This is the same ruinous mistake made by so many populist-nationalist leaders down the decades. The great flaw of nationalists everywhere is an assumption that their nation has greater political, economic and military potential – and their rivals less – than is really the case.

Exaggerated ideas of national superiority have fuelled the most self-destructive policy mistakes of modern European history. They led to France declaring war on Prussia in 1870 and Germany choosing to fight wars on two fronts in both World Wars. American and British leaders blithely intervened in Afghanistan and Iraq this century in total ignorance of the real odds against their success.

Such military examples are apposite because Britain’s withdrawal from the EU is the equivalent of a major defeat in war. Suppose, hypothetically, that Britain fought and lost a military conflict with a rival European power, then the departure of Britain from the EU might well be demanded by the victor as a way of ensuring that Britain was permanently weakened.

What foreign enemies failed to accomplish against the British state for centuries may soon be inflicted by the modern day Jumblies. Negotiations now completed are at best an attempt to mitigate the extent of the British loss and all scenarios point to a country less well-off and influential than if it had stayed in the EU.

The best argument for Brexit has little to do with political power or economic success. The demand for national self-determination has been behind the most progressive developments in the world over the last century since the break-up of the German, Austro-Habsburg and Ottoman empires after 1918, and the British and French empires after 1945.

Newly emergent nation states invariably blame former imperial masters for their economic, political and social troubles. Usually there is a lot in this claim, though not as much as the claimants pretend. In this context, there is nothing surprising in the fact the British complaints against Brussels echo those made by the Irish and the Indians against London when they fought, with rather more reason, for their independence.

This comparison will not appeal to hardcore Leavers because of their nostalgia for a state of the world at home and abroad that, if it existed at all, was briefly present in the 1950s. British society of that era may have some aspects that were superior to the present, as well as many that were worse, but in either case they lie in the past and cannot be recreated.

One of the many weird characteristics of the Leave leaders is their frequent references to a mythical version of British history, featuring “vassalage” and humiliating treaties signed by King John at the beginning of the 13th century. One Brexiteer even attacked the proposed EU agreement as the most humiliating since Charles II agreed the Treaty of Dover with Louis XIV in return for a heavy subsidy in 1670.

But these historical nuggets are really only there for adornment. For all the talk about “Britain standing alone”, Britain invariably made every effort to do no such thing. British success against Napoleon, the Kaiser and Hitler were based on the Royal Navy preventing defeat, while Britain built up overwhelmingly powerful alliances against the enemy of the day. The last time the country was as bereft of continental allies as it is today was during the American War of Independence at the end of 18th century.

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Contemporary English populist nationalism has much in common with similar movements in Europe and the US: hostility to immigrants and minority communities combined with a sense of lost identity and control, which seems to be the inevitable consequence of globalisation.

For globalisation in this century is turning out to be as destructive to the political and social status quo as the Industrial Revolution was in the 19th century. Metropolitan areas, primarily urban, that are plugged into the global economy do well, while everybody else falls behind or does badly. The same pattern is repeated everywhere from Arkansas to the Isle of Thanet and from Saxony and the rural hinterland of Damascus.