The BREXIT vote:
pro-leave campaigns
showed
POST-TRUTH POLITICS
                 AT ITS PUREST

The Brexit campaign period showed how an ecosystem of official campaigns, outriders, friendly press and social media can work together to amplify messages to groups receptive to them and how if a central campaign stategically distorts the TRUTH it can serve as a huge advantage.

Source:[5]

Arron Banks, the businessman who bankrolled the Leave.EU campaign, was correct in his analysis of the referendum outcome:

The Remain campaign featured fact,
                                               fact,
                                             fact,
                                           fact.
It just doesn't work.
You've got to connect with people emotionally.
It's the Trump success.

Those pressing for Britain's continued EU membership bombarded the public with statistics: leaving would cost 950,000 UK jobs,
                              the average wage would fall by £38 a week,                               each family would pay an average of £350 a year more on basic goods, £66 million a day invested by EU countries in the UK would be at risk, the cost of leaving would be £4,300 per household... and so on, and so on.

It became easy to caricature this torrent of indigestible data as no more than a series of arbitrary claims.

What the Brexiteers understood was the need for simplicity and emotional resonance: a narrative that would give visceral meaning to a decision that might otherwise appear technical and abstract.

As Dominic Cummings, campaign director of Vote Leave, argued at the time, the case for departure had to be clear and cleave to the specific grievances of the public. A message based upon the trade opportunities of Brexit – GO GLOBAL – might be intellectual defensible but it would not win votes. Earlier research by Cummings on Britain's potential membership of the euro had revealed the potential traction of a pledge to Take Back Control.

Second,he believed that the weekly cost of EU membership – allegedly, £350 million – should be front and centre in the campaign and, crucially, identified as a dividend for the National Health Service.
In other words: subsidise doctors and nurses, not Brussels bureaucrats.

Third, the campaign should present the potential accession of Turkey to the EU as a clear and present danger to Britain's control of immigration policy.

The various leave campaigns were content to unleash soaring expectations among those who chose to blame their misfortunes -real or imagined - upon immigrants. Though Turkey's membership of the EU was a remote prospect at best – as the European Commission's latest annual report on its progress makes clear – it suited the Brexiteers to stoke fear of its accession and a consequent wave of Muslim migrants.

This was Post-Truth politics at its purest – the triumph of the visceral over the rational, the deceptively simple over the honestly complex.

No less spurious was the assertion – emblanozed on the side of the Leave battles bus – that Brexit would yield a £350 million weekly top-up for the cash-strapped NHS (National Health Service). For a start, the pledge did not take account of the rebate received by Britain: its net contribution per week to the EU was closer to £250 million.

Having pointed out the error, the UK Statistics Authority declared itself 'disappointed to note that there continue to be suggestions that the UK contributes £350 million to the EU each week, and that this full amount could be spent elsewhere'.
But the Leave campaign proceeded, unabashed.

Source:[1]

The £350 million claim was cited daily in the media, was raised regularly by serving Cabinet ministers, and appeared in the visuals of almost every piece of Brexit coverage thanks to being printed on the side of a bus. And yet almost no one who said it could possibly have believed it to be true: as the months after the vote made clear, virtually no one at the core of the Vote Leave campaign believed in the literal truth of the campaign's central slogan.
There would not be £350 million a week for the NHS.

During the campaign, Boris Johnson, then a Cabinet minister and now the the Foreign Secretary, posed in a high-vis jacket with a giant £350 million cheque at a blast furnace in Staffordshire, before symbolically burning the cheque.

A third cabinet minister, Priti Patel, tied together the £350 million figure and immigration in remarks to the Sunday Telegraph.

She said,
It is becoming clear that our membership
of the EU is putting the NHS under threat.

Every week we send £350 million to Brussels – that's money that could be better invested in helping patients who rely on our NHS... Current levels of migration are causing unsustainable pressures on our public services and we can see that the NHS is creaking under the strain.

Vote Leave's campaign director Dominic Cummings knew exactly what he was doing, as he set out in a lengthy blog post months after the campaign was over. Stating that the £350 million NHS claim had been necessary to win.

Cummings explained:
Sometimes we said ‘we send to EU £350 million’ to provoke people into argument. This worked much better than I thought it would. There is no single definitive figure because there are different sents of official figures but the Treasury gross figure is slightly more than £350 million of which we get back roughly half...

Would we have won without £350 million/NHS?
All our research and the close result strongly suggest NO.

Source:[5]