Opinion: commercialisation of the UK's architectural heritage helped lay the foundations for the false nostalgia that is proving such potent propaganda for Brexiteers, says Sam Jacob.

Part of the problem with the EU Referendum is its slippery nature. What exactly are we voting for? What does it really mean? How will it change things? How will the country feel if we exit the European Union?

Well, to give you an idea let me take you to the supermarket. For it is there amongst the aisles that we find a parable on the complexities of national identity in the modern age.

Woodside Farm. Just picture it: branches blowing in the wind, the cooing of a wood pigeon, a pile of logs and a weathered shiplap barn. Or Willow Farm: the gurgle of that stream where the fronds of the tree hang in the water as the sun sparkles, perhaps Ratty and Moley rowing past. Oh yes, Redmere Farm, where the bracken is already turning, the flash of a hunter's jacket, the shallow depths of the lake broken by bullrushes...

But before you get carried away with soft-focus images of the British landscape I should tell you: Woodside, Willow and Redmere Farm are all imaginary places, a few of the fake farm brands imagined by supermarket giant Tesco as a way to package meat and fresh produce. Brands that conjure an image steeped in a nostalgic dream, that suggest a relationship to land, soil and place, that heavily hint at provenance and stewardship. Of course, wrapped inside them is something else.

Woodside Farm products, according to a spotcheck by Farmers Weekly, contained pigmeat products from the UK, Holland, Denmark, Germany and "the EU". Redmere contained an even more international cocktail: sprouts (UK), mushrooms (Holland), carrots (UK), parsnips (UK), spinach (Italy, Spain), spring greens (UK), cabbage (Spain), onions (UK), new potatoes (UK), sweet potatoes (US). Willow Farm chicken, at least this time, proved 100 per cent British – though how much a single farm distributed nationally chimes with the apparent image is another question.

Right there, fondling a pack of sausages we find ourselves pondering more than tonight's dinner. Those sausages are squirming and seething with the complexity of contemporary culture, the perfect metaphor for the EU Referendum.

What's at stake in the referendum is ideas of globalisation, identity and authenticity. Listen to Leave, who claim Brexit means "taking control", means making Britain "great" again, means regaining sovereignty. Leave is the promise of the fake farm – the nostalgic image of a country where we can finally become ourselves once again, but one that doesn't exist.

The history of Britain is one not of glorious isolation but of continual engagement with the wider world. The most ancient landscapes of Neolithic Britain are scattered with the work of the pan-European Beaker People, Celtic druid culture, Roman cities, Anglo Saxon settlements, Viking kings, Norman Castles – the landscape of the nation is a palimpsest of European-ness.

Our cities are built with the wealth of global imperialism, our population in wave after wave from any number of "elsewheres". The history of Britain is one intimately interwoven with the world.

The symbols deeply embedded in our psyche as national are symbols not of "here" but "everywhere". Indeed everywhere we look for "Britishness" we find things that unravel into internationalism: St Paul's Cathedral (Italian Baroque + post Civil War England), the landscapes of the picturesque (European landscape painting + aristocratic power), punk (French theory + pop sensibility). Hell, even (especially) the Royal Family.

These are things that embody not our isolationism but our deepest connection to Europe and the world. Indeed, British culture is perhaps best understood as an alchemic thing that can fuse diversity into something new. The idea of distancing ourselves from exactly that which has made Britain so culturally rich is not only a rejection of the facts of history but a surefire way to diminish the future of our cultural life.

This false nostalgia is not unique either to this referendum or to Britain. It's a scenario that has been played out again and again as nations have wrestled with the challenges of geopolitics. Right now, it's being played out in the US presidential campaign as Trump declares he will "make America great again". It is also visible across Europe.

Across the west, across Europe, old-fashioned ideas of nationhood are rising, where identity, rhetorics of freedom and increasing xenophobia merge with the fear of the future and the "other". In other words, as modernity inexorably engulfs us, we react by fetishising the local.

Being "local" is a way, we feel, to counter the forces that rage around us, the forces that are transforming economies, social structures, landscapes, cities and lifestyle.

But modernity is not something that can be warned off with fetish objects, with heritage tomatoes or with navy passports. We know full well that even the concept of the nation state is unable to fully contend with, say, global corporatism or the liquid capital that flows through the networks of international banking, the information networks that flow regardless of borders, the planetary issues of climate change and so on.

The myth that is touted as the solution is never real. The nostalgia we all feel is for something that never existed. Yet its power remains very real.

In the UK, a particular and specific form of politicised nostalgia has emerged. One that has driven the right wing of the Conservative party since the early 1980s, and has become so powerful as to engulf the entire country and precipitate a sense of crisis so immense as to bring about this referendum.

At the end of the 1970s, Britain found itself a post-colonial, post-industrial state. Elected on a free-market platform, Margaret Thatcher's party set about a radical reorganisation of British life.

Deregulation and privatisation would set the country free from its dependency on government and the welfare state, so ran the argument. Entrepreneurship and individuality would, it was said, be liberated to restore the country to its former glories. Yet the reality was that these policies were deeply divisive.

As the clashes of the Miners' Strike raged, as places like Toxteth and Brixton rioted, the country bathed itself in the glow of Merchant Ivory films staging British culture as autumnally hued historical mannerism.

In architecture, this nostalgic urge drove polarised schisms between traditional and Modernist approaches that culminated in Prince Charles' Vision of Britain, his pseudo-vernacular "village" of Poundbury (ironically, a place only rivalled by Docklands in its sense of North American-ness). At a governmental level, similar veins of nostalgia became central to policymaking.

Heritage was reimagined as a new revenue stream. The old body concerned with preservation was first streamlined into English Heritage, then tasked with finding ways to raise funding. Heritage became one of the new commodities of post-industrial Britain, history as an academic or factual thing transformed into consumable, sellable stuff. Even as the mines and plants of industry were being shut down, ye olde England was being packaged as a product that could be sold alongside post big-bang financial services.

The mode of historical re-enactment in the 1980s became so powerful as to be a device that could at once summon a warm sense of nostalgia while also delivering a radical shift to the neoliberal form of late capitalism. Thatcherite policies used nostalgic images to assault the traditional structures of state and society: a futurism fuelled by an imaginary past.

This, of course, is the deep irony of the Leave campaign. That it stages its complaints against a straw man of modernity that it characterises as faceless EU bureaucrats when really, our complaints are towards the deregulated, unaccountable fiancialisation to which it was originally nursemaid.

And we live now within these logics – stewed on backbenches over a generation until they have emerged on the centre stage of contemporary politics in ugly, gruesome form. The nostalgic genie, out of the bottle, is now not only the sugar for the pill but the pill itself.

The perversity of the movement runs deep. Facts are trumped by sentiment, as Michael Gove made clear when he said: "I think people in this country have had enough of experts."

Its propaganda is that of the conspiracy theorist. When it talks of fear, it means fact. When it talks of common sense, it means fantasy. When it talks of freedom, it means tyranny. When it talks of traitors, it assaults democracy. This is politics through the looking glass, where white is black and black is white and truth evaporates into a mist of diversion and deceit.

Vote Leave argues that we can no longer trust our mainstream politicians, while itself redrawing the line of what was once called "being economical with the truth".

Yet Leave's argument is powerful despite (or because of) its rejection of facts. However perverted, it remains such an attractive sentiment, a fantasy so strong that half the country believes we might be able to vote ourselves into a fiction. And let's be frank: who wouldn't want to do that? To exit the realities of the modern world and enter a world of Woodside Farms, where we can act – or rather reenact – an idea of Britain.

We now are at the border of Brexitshire, and if we choose to enter we'll find it a place where fiction runs backwards into reality. A place where we might cast ourselves as Downton Abbey characters in a pseudo-Britain manufactured from of a scrapbook of historical misquotes.

Vote Leave is a vote for a theme park instead of a country. Vote Leave is a vote for the replacement of state with a pageant of empty symbols. Vote Leave is a vote for a country of fake farms, a place defined by a synthetic and cursory branding of Britishness every bit as cynical and empty as Tesco's packaging.

Main photograph of Poundbury by Richard Dorrell.

Sam Jacob is principal of Sam Jacob Studio, professor of architecture at University of Illinois at Chicago, director of Night School at the Architectural Association, and the editor of Strange Harvest.