An artwork in the lobby of the Berlaymont, the European commission headquarters in Brussels, has 12 gold stars in a circle on blue canvas; the stars are shaking, literally in a state of agitation. It is, the label says, a mixed media representation of the European flag dancing for joy.

Thursday’s election will, Boris Johnson hopes, resolve Britain’s neuralgic Europe question, letting him take the UK out of the EU on 31 January. The formal end of membership, if Johnson wins, should after 46 years feel seismic – one of those gold stars falling out of the constellation. But in the place where Johnson – as a Daily Telegraph correspondent in the early 1990s – did so much to debase the EU’s virtues, things have moved on. Britain has never been so obsessed with Europe, but the EU has already left Britain.

If the curtain was really about to fall, I wanted to remind myself of how Johnson's revolution took hold

I was in Brussels too, in those years, reporting on, among other things, the birth of the EU’s most ambitious and possibly ill-conceived idea, the euro. And before our eyes, Johnson hatched the stories that seemingly incubated this ending and the shockwaves that will follow. The 2016 UK vote to leave was not entirely about Europe. But Brexit as a promise that British politicians are now expected to honour – even if it makes no sense – is in part the rejection of a mythical “Europe” that came to life in these buildings in the mid-90s.

With so many certainties about to be upturned, I returned to Brussels last month. If the curtain was really about to fall, I wanted to remind myself of how Johnson’s revolution took hold.

In the 90s, journalists from all over Europe and beyond came to the Berlaymont every day for the commission’s noon press briefing. The subject-matter was dry stuff. The lifeblood of the world’s greatest experiment in peaceful cooperation, it turned out, was dairy quotas and steel tariffs. No wonder everyone clustered around the salle de presse coffee bar, trading gossip and information. Or that the high politics – the tensions between prime ministers or between “Brussels” (the commission) and the capitals – made what we thought were the most relatable stories.

Johnson is now, rightly, held responsible for much of Britain’s neurosis about the EU. But could he alone have brought us to this point? Was there a broader negligence or even complicity? And does the emphasis on his role minimise the difficulty of communicating any big political idea to an indifferent public?

Back in today’s modernised Berlaymont press area, I ordered coffee from Nelson, who has been working here for nearly 25 years. Would he miss the Brits if they go? “It’ll be different,” he said. “The British asked the hard questions.”

It is true that the British media highlighted the absurdities from day one. As the former PA correspondent, Geoff Meade – who arrived to cover the European Economic Community in 1979 – reminded me, there were wine lakes, butter mountains and Strasbourg gravy trains to lament. The organisation’s complexity, and its novel but poorly understood structures, made it an easy target.

Boris Johnson at a house party in Brussels in about 1990 during his time as Daily Telegraph Brussels correspondent. Photograph: Charles Grant

The difference in the 90s was that the regulatory “harmonisations” of the single market were being rolled out. Even if by then overzealous officials spreading red tape was an established trope, the single market provided a rich new seam. Johnson weaponised it. From “edicts” (the language itself was a distortion) about bananas grew a dishonest and xenophobic campaign about British democracy. (Johnson’s high point, by his account, was a fictitious ban on British prawn cocktail-flavoured crisps, in which the culpable German EU official, Martin Bangemann, became known in UK tabloids as the “Sour Kraut”.)

Whether Johnson believed it or not, the narrative he sold was that elites on the top floors of the Berlaymont were engineering a federal superstate in which Jacques Delors would eventually “rule”.

Tragically, UK governments – of every stripe – colluded with the tabloid presumption that an outraged British public would view any EU regulation as Johnny Foreigner robbing them of their freedom. John Major had the Tory Eurosceptics on his back. But Labour ministers after 1997 used to spoonfeed spurious lines to the London press about “battling” before travelling to Brussels. It made sure that whatever they agreed, the fictional British “victory” would be the news. Those Labour ministers supported the overall vision but ran scared of explaining it. Would we be in a different place now if British people had been permitted to consider, in detachment, if they wanted clear labels about E-numbers in crisps or rules on clean water?

My return to ground zero reminded me of something else: in 90s Brussels, Johnson’s lies weren’t taken all that seriously. Lurking at the back of the press room, I had uneasy flashbacks to the chief spokesmen (they were nearly all men) grinning indulgently at the interventions of “Boris”. If they were appalled about either his superstate scaremongering, or that his main beef with the EU was that it balanced the interests of workers or consumers against big business, they didn’t show it with any force.

The Berlaymont building, pictured in 2015. Photograph: Etienne Ansotte/EU/Shimera/Etienne Ansotte

It was a broader failing too, that news about the EU was almost entirely filtered through a domestic lens. In the absence of a common European “demos” or identity, governments took their national concerns to the EU table, and that’s what got fed back via us in the media. I started out reporting EU news for an Irish paper. There was little appetite for Euroscepticism. Irish public opinion saw “more Europe” as a good thing. But unless the Dublin government had secured another slice of funding or was being shamed by Brussels for its inaction on something, editors weren’t that interested.

The annual battle over fishing catches showed the system at its parochial worst: for PR purposes national governments would negotiate through the night. The outcome would get written up either as a disaster or a “bonanza” (the UK or Spanish trawlermen waiting outside would tell us which). The common interest in protecting fish stocks got drowned out. Perhaps UK ministers’ cowardly refusal to own Britain’s place in the EU had its genesis in a legitimate difference of approach. Britain saw the EU as transactional, so wanted an impossible reassurance about the endpoint of membership. Continental governments saw the EU as transactional too, but also as strategically vital. Either way, by the 2016 referendum campaign it was about 20 years too late for British politicians to start telling people what the EU was for, let alone making a high-minded case for it.

The 90s manipulation of British public opinion predated ideas of fake news or Dominic Cummings. But it foreshadowed today’s mythologising of the regulatory “freedom” that Brexit supposedly justifies.

I was struck by how, when campaigning to become Tory leader this summer, Johnson suddenly produced a packet of smoked kippers and lied about EU rules forcing the kipper producers to use pillows of ice for packaging. “Boris” had gone back to the 90s, to revive his hostile old narrative. Go to Brussels now, and Brexit feels like a ship that has sailed. UK ministers have not been seen in certain councils for months. “It’s like a death in the family,” a Swedish veteran told me. “You keep going, but it’s not the same.” Britain’s last commissioner, Julian King, physically left the Berlaymont for the last time on 29 November, taking his union jack cushion with him.

Britain’s chaos has opened eyes about what disentangling 40-plus years of integration looks like. Democracy may be failing in Poland and Hungary, and the Franco-German axis may be fraying, but public support for the EU is higher than it has been for years.

Johnson’s promise that a new EU-UK relationship will be complete by December 2020 is ridiculous. The imbalance is startling: the EU side will have 700 experienced negotiators for trade, and hundreds more from financial services, fisheries and judicial cooperation. Far from dancing for joy, nearly everyone I met spoke of the impending rupture as a “tragedy” or “aberration”.

And how will the EU be discussed in “free” Britain after Brexit “gets done”? My guess is Brexiteers will spend the next 10 years scapegoating the treachery of a Europe whose “edicts” made sure the Brexit they got wasn’t the Brexit of their fantasies.

• Katherine Butler is the Guardian’s associate editor, Europe