WORRYINGLY, it appears there remains a jaw-dropping lack of arithmetical perspective around the UK’s Brexit crusade.

Of course, the UK Government’s exit from the European Union is all about ideology. And politics is politics. So you would expect the Boris Johnson Government, with its big majority and Brexit-loving Cabinet, not to mention adviser to the Prime Minister Dominic Cummings doing whatever he does, to spin the various developments around this to whip up that British nationalist fervour that has delivered their goal of separating from Europe. It has worked a treat for them so far with Brexit voters.

But this rambunctious and patriotic tub-thumping does not mean that what is reality and what is fantasy have in any way changed.

Fairly predictably, the UK has, after its toys-out-of-the-pram incident the week before last, decided that it will continue talks with the EU on a trade deal.

It is difficult to see what in the real world has changed specifically or materially on this front. A statement last Wednesday from 10 Downing Street on the resumed talks seemed to paint a picture that EU chief negotiator Michel Barnier’s address to the European Parliament had provided reassurance that Britain’s sovereignty was being taken sufficiently seriously.

The UK side has repeatedly shown signs of going off in a huff when it has perceived the EU is not making a big enough deal of Britain’s sovereignty. So maybe that is it – that a perceived (and probably imagined) slight is seen as having dissipated and talks can restart.

Or perhaps the threat to walk away from the talks was a somewhat desperate negotiating tactic, at the same time playing to the noisy gallery of Brexiters.

The Conservative Government continues to bang on about UK sovereignty and independence, which were surely never in question as part of the EU. Back in the real world, away from abstract ideology, businesses and households try to brace for the effects of the eventual Brexit outcome, which remains up in the air with little more than two months to go to the end of the transition period.

Nothing much seems to have changed for many months in the UK’s talks with the EU.

The statement from Downing Street declared: “It is clear that significant gaps remain between our positions in the most difficult areas, but we are ready, with the EU, to see if it is possible to bridge them in intensive talks.”

Big differences in the talks have related in large part to the level playing field requested by the EU, on issues such as state aid and food and product standards, and fisheries. Brexiters appear to have seized upon fisheries, and access to UK waters, as a most emotive issue with which to whip up British nationalism.

What is new in the negotiations is a detailed plan of how the talks will be conducted as the clock ticks down.

Downing Street talked about having “jointly agreed a set of principles for handling this intensified phase of talks”.

Agreement on points of substance might be much more reassuring at this stage.

Meanwhile, Downing Street offered what seemed like a realistic assessment in terms of continued huge uncertainty over whether a deal can be concluded or not, although there will likely also be an element of negotiating posture in this.

It said: “As both sides have made clear, it takes two to reach an agreement. It is entirely possible that negotiations will not succeed.”

What seemed far less realistic was Downing Street’s assessment that the UK would “prosper” through a no-deal outcome. The UK Government’s preferred “Australia” analogy was trotted out again to describe a no-deal result. It is difficult to know whether this is a euphemism or meant to stir up passion for the Commonwealth, or both, or neither.

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Whatever the case, the upshot remains that UK businesses and households will have to use their valuable time to prepare for a no-deal outcome.

Of course, the latest “time is running out” phase of the UK Government Brexit information campaign, including television adverts, is making it perfectly plain that businesses and households will face myriad hassles whatever the scenario come December 31. More is the pity.

This is because nothing much changed when the UK Government got its technical Brexit on January 31. The transition period, which runs out at the year-end, has protected the UK from the actual effects by keeping it a member of the European single market.

Sadly, the realities are about to kick in, at the worst time possible amid the coronavirus pandemic, whether the UK achieves the relatively narrow trade deal it is seeking with the EU or not. Of course, a no-deal outcome will be far worse still, but the effects of leaving the single market, and losing truly frictionless trade and the huge advantages of free movement of people between the UK and EU countries, will be grim either way round.

And this is where we get to the arithmetical realities of the situation.

Last week, the UK signed a free trade deal with Japan.

And the Johnson Government seemed to be falling over itself to thumb its nose at the EU as it did so.

It hailed the agreement with Japan as “the UK’s first major trade deal as an independent trading nation…offering a glimpse of Global Britain’s potential”. Note the “Global Britain” – with an initial capital on “Global”. You could almost hear the tub-thumping as you read this “world news story” published on the Government website on Friday.

And it did not stop there.

We had this from Secretary of State for International Trade Liz Truss: “Today is a landmark moment for Britain. It shows what we can do as an independent trading nation, as we secure modern and bespoke provisions in areas like tech and services that are critical to the future of our country and the reshaping of our economy.”

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Ms Truss appeared at pains to talk up the “bespoke” provisions in the UK-Japan deal.

There is no doubt that Japan is a hugely important trading nation on the global stage.

However, while it is a relief that the deal has been done, it is crucial to realise that the agreement essentially mirrors the one which Japan implemented with the EU last year.

That is to say, for all the fanfare with which the signing was greeted last week, by Ms Truss and other Brexiters, it is important to recognise the UK is not gaining anything significant which it would not have had as part of the EU.

The Brexiters promised a raft of big new free trade deals enabled by the UK’s departure from the EU. Years later, these have yet to materialise.

The other crucial point to consider is the projected benefits from the Japan deal, and indeed from the trade agreement being sought by Ms Truss and her Cabinet colleagues with the US, relative to what Johnson and Co are doing to UK GDP and living standards with their Brexit odyssey.

The UK Government says the “estimated boost to trade between the UK and Japan is over £15 billion”. This estimated fillip is on a 15-year time horizon and equates to a £1.5bn or 0.07 per cent boost to UK GDP.

We hear chatter about there being a view in some European governments that Mr Johnson might be waiting to see if his Brexit-supporting ally Donald Trump wins the US presidential election before making a final call on deal or no deal with the EU.

Who knows if this is the case. In any event, however, Mr Johnson should remember the Conservative Government noted in its own paper on its sought-after trade deal with the US that such an agreement could, in the longer term, boost UK GDP by around 0.07% or 0.16% under two different scenarios.

He should weigh the numbers on the US and Japan deals against the forecasts from the Theresa May administration, published in November 2018, of the detrimental impact on the UK of Brexit and crucially of leaving the European single market.

These 2018 projections show, even if there is no change to migration arrangements, UK GDP in 15 years’ time under a no-deal Brexit scenario would be 7.7% lower than if we had stayed in the EU.

The Tories, of course, plan to clamp down on immigration dramatically, and have legislated to that effect. On the basis there is zero net inflow of workers to the UK from European Economic Area countries, the forecasts from the May government have it that GDP in 15 years’ time would in a no-deal exit be around 9.3% lower than in a scenario in which the UK had remained in the EU.

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If the UK were to conclude an average free trade agreement with the EU, the hit to GDP would be 6.7% on the scenario of zero net inflow of EEA workers, according to the forecasts. And even with no change to migration arrangements, which is now clearly an over-optimistic scenario, the hit to UK GDP with the securing of an average free trade agreement is 4.9%.

We also had this from Ms Truss on Friday regarding the deal with Japan: “Trade is a powerful way to deliver the things people really care about. At its heart, this deal is about creating opportunity and prosperity for all parts of our United Kingdom and driving the economic growth we need to overcome the challenges of coronavirus.”

She also talked about how the deal with Japan “opens a clear pathway to membership of the comprehensive Trans-Pacific Partnership – which will open new opportunities for British business and boost our economic security”.

Trade can help deliver prosperity.

And the UK was perfectly placed on this front, as a member of the biggest free trade bloc in the world (larger than the distant TPP), before the Brexiters rode into town.

Whether the UK secures a narrow free trade deal with the EU or not, leaving the European single market will drag the British economy down dramatically for many years to come. This overall reality will not be changed by the Japan deal, or a US agreement for that matter.

It does not matter how you spin it. The numbers tell the story.

What the UK Government is actually doing is delivering a very costly Brexit, which will compound massively the huge damage to the country’s economy from the coronavirus pandemic.