I wonder what in 100 years from now it will be, London. The city that privatised itself to death. Abandoned to nature, maybe, the whole place a massive, feral version of that mimsy garden bridge over the Thames currently being planned by the giggling classes. Poor London, the ancient and forgotten metropolis, crumbling slowly into an enchanted urban forest.

Imagine. In 2115, all the lab-conjured animals in Regent’s Park Jurassic Zoo are free to roam, reliving their evolution. A diplodocus there, grazing in the jungled Mall. Look, a stegosaurus asleep in the ruins of Buckingham Palace. High above the forest canopy, a lone archaeopteryx soars, where once hundreds of drones glided through YouTubed firework displays.

Perhaps eminent historians will study London in the early 21st century, see how its poorer inhabitants were driven out, observe how its built environment was slowly boiled to death by privatisation. And they will wonder why people tolerated this transfer of collective wealth from taxpayers to shareholders. And they will perhaps turn their attention to Eduardo Paolozzi’s fabled mosaics at Tottenham Court Road underground station.

Back in 2015, a debate has bubbled briefly, after some of these lovely, publicly owned mosaic murals were quietly dismantled as part of the station’s thorough £400m Crossrail seeing-to. I say “debate”; it was really only that polarised quackbait thing we have now: Click If You Think The Mosaics Are Great, We Should Save What’s Left Of Them v Smash Them Up They’re Ugly, Anyway Who Cares It’s Just Patterns On A Wall.

Arguments about the aesthetics of Paolozzi’s mosaics missed the point, it seemed to me, which has less to do with the merit of the art itself and more to do with what, in the long run, it turned out the art was for. Paolozzi’s legacy had stood intact for three decades. Not just as 1,000 sq m of charming, optimistic art, but as 1,000 sq m of commercial retardant.

You can’t paste an ad on to a wallful of public art. You can’t fix one of those irritating micromovies over it, telling a vacuous five-second story about investments or vitamins or hair. The Paolozzi mosaics went up as decorative art, just as privatisation was about to explode like a dirty bomb all over the public realm. What survives at Tottenham Court Road station is a brave, forlorn little seawall set against a stormtide of corporate advertising.

Part of Eduardo Paolozzi’s mosaic at Tottenham Court Road underground station. Photograph: Sarah Lee

1982 it was, when those mosaics were unveiled. British Petroleum had already been privatised. British Aerospace, too, and a slew of others. The right to buy had been introduced a couple of years earlier. Still to come: BT, ports, buses, British Leyland, British Steel, Rover, gas, electricity, water, the railways. All those non-coloured Monopoly cards? Wait, wait, you can’t privatise those, they’re public utilities, clue’s in the name, oh, too late. It was a free-market frenzy. Everything we owned was being flogged off by pinstriped bastards reeking of lunch.

What survives at Tottenham Court Road is a brave little seawall set against a stormtide of corporate advertising

I say “we”, although the greatest trick Thatcherism ever pulled was this redefinition of “us and them”. Suddenly, people in your own family were voting Tory. Mrs Thatcher’s chief information officer, Rupert Murdoch, was telling us that the firemen and the dustmen were our enemies. That the women of the NUT and Nalgo were the mad, selfish defenders of a doomed elite. The Tory government went after the local authorities, telling us that government itself was our enemy. You were just going: “Hold on a minute, if you’re the government …” and then they shouted: “Oh, God, look! The Falklands!”, hired more expensive PR guys and carried on privatising. All through the reign of Margaret the Baby-Eater. Through John Major’s steady-as-you-go age of dinge. And into the sunlit uplands of Blairvana where, ingeniously, the government launched a full-scale privatisation of the future: the public finance initiative. Of all the Tory policies adopted by the Labour government, none was Torier than PFI. This policy wore a black cape and a top hat. It twirled a moustache and cackled. “Oh, you’d like a hospital? Allow me to build one for you, no charge. Just rent it back from us for, let’s say, 50 years, plus service charges; exactly, minister, why worry, you’ll be out of the cabinet and on our board soon enough. Waiter! We’ll see the pudding menu now …” Instead of snapping this brittle cack in half and binning it, Labour embarked on a massive PFI expansion. Now our children owe billions to PFI shareholders, and it’s no consolation at all to think that our grandchildren will, too.

But there was a time when “we” were winning. The “we” I always understood to be “us”, that is. The collective us. Before the privatisation of air and space. Let me tell you, little ones, about how popular music and the bright optimism of collective space came together long ago in London’s heady, soot-laden, pre-privatised air of 1967. Song of the summer was Waterloo Sunset by the Kinks, with its odd blend of keening melancholy and positivism. Nostalgia for a doomed postwar world, exhilaration for the coming of a new post-industrial one. Terry and Julie, facing the future unafraid. Wherever you went, it floated into earshot on a tide of treble from someone’s transistor radio.

And if you were Terry and Julie gazing at a Waterloo sunset in the summer of 67, you’d have seen the Hayward Gallery under construction. The beautiful, brilliant, brutalist Hayward, part of a people’s South Bank that had started with the Festival Hall in 1951 and would end triumphantly with the National Theatre in the 1970s. And we did gaze at it, thinking: “This is us.” This is us, building something amazing, for us. Several eminent architects worked on the scheme, but oversight belonged to the GLC architects department. Imagine that. A time when most architects worked in the public sector, designing a world of public space and collective aspiration, a world of affordable housing with statutory space standards. Crazy days, when a giant yellow Aviva ad on the NT’s western wall was unimaginable.

Then, suddenly, architecture, like everything else, was privatised. The 1980s saw deregulation, not only of the financial markets, but also of the professions. The number of local-authority architects plummeted under a regime of cuts; the harsh winter of recession in 1990 finished them off. From now on, space and air would be shaped and primped by the private sector. Architecture was redefined: no longer frozen music, but petrified Thatcherism. The client’s brief was to choke as much value out of a site as possible, and the model was Broadgate. That shoulder-padded yuppie citadel, which unlocked so much subsequent property value in east London. It seems so weird that it’s old enough now – 30 years – to be listed as a historic building itself, even as it continues to grow, ever more offices cramming in, and a fortune being made from it, somewhere, by tanned people with watchful lawyers.

Very few people now remember what was there before – Broad Street railway station and its environs. The station architecture wasn’t particularly distinguished, but that wasn’t the loss. It was the space, 32 acres of nationalised space and air, once managed by us as a part of a nationalised industry.

Broadgate looks great in photographs, particularly in night shots. The little central public space, the little public ice rink. Lovely. But this space was and remains a concession, a “planning gain” to sweeten the deal. Look, nobody’s suggesting that Broadgate should have been a 32-acre ornamental garden, as attractive as that sounds. Wait, actually, yeah: public gardens would have been fantastic, come to think of it. However, of course the city needs offices. And Arup’s Peter Foggo, highly regarded in the profession, designed much of Broadgate. It looks pretty good, which is why the architectural historians want to save it.

But it has nothing to do with us, does it? It’s privatised space and air. Broadgate became a template for capitalism. Broad Street station, British Rail, everything we owned at the time was sold off cheaply to developers, who then sanctimoniously sold us back this narrative of humane regeneration and philanthropy. Hire an eminent architect, stick a public garden in the middle, bosh. Done. We swallowed the lot. Loadsamoney, planner-friendly, enlightened patronage. Suddenly entrepreneurs were “patrons of the arts”. Of course they were. That’s where the money was.

Broadgate: ‘a shoulder-padded yuppie citadel’. Photograph: Bloomberg via Getty Images

And as more of what used to belong to “us” was sold off and developed by “them”, the hunger for floorplates and square footage and award-winning design and river views became insatiable. If they ran out of land to build on, no problem. They would now literally monetise thin air. The principle of “air rights” development in London was nailed by architect Terry Farrell’s Embankment Place. A client could commission a great design saturated with Farrell’s trademark postmodern wave-it-through-planning magic, acquire the air rights above Charing Cross station and whack a massive office block on the roof. Ingenious. A private incubus squatting on an anaesthetised public space.

If they ran out of land to build on, no problem. They would now literally monetise thin air

Bit by bit, the city has been handed by us to them. It’s now acceptable for the privatised space of a shopping centre to be patrolled by private security. There are enforceable dress codes, which is a laugh, considering those ill-fitting security uniforms. No loitering – another hypocrisy, as that’s pretty much 100% of a security guard’s job. They’ll all have Tasers soon. A 2011 London Assembly report – Public Life in Private Hands: Managing London’s Public Space – said the mayor of London was concerned that “there is a growing trend towards the private management of publicly accessible space. Where this type of ‘corporatisation’ occurs, especially in the larger commercial developments, Londoners can feel themselves excluded from parts of their own city.”

That’s Boris Johnson there, the freewheeling ultra-Tory ox. Like me, like us, he’s having an emotional reaction to witnessing the very fabric of the city, and the air around it, and the economy around that, being aggregated into some vast equity milking parlour by the very arseholes who smashed everything to bits the last time. Obviously, the mayor simply wants them to behave in a more gentlemanly fashion, whereas some of us want them roughly arrested, electronically tagged and confined to their extinct volcano lairs, but it’s nice to know we’re on the same page.

Oh, man, and just look at London’s privatised skyline. It would be hilarious if it wasn’t so cartoonishly tragic. This one looks like a Nespresso machine. And that one, a cigar, is it? Potato? Full nappy? The utter capitulation of London’s planning system in the face of serious money is detectable right there in that infantile, random collection of improbable sex toys poking gormlessly into the privatised air. Public access? Yeah, we’ll definitely put a public park at the top (by appointment only). Oh, absolutely, we are ALL about community engagement: members of the public are welcome to visit our viewing gallery in the sky, that’ll be 30 quid, madam.

The great modernist architectural mantra is “form follows function”. I think we can safely call time on that one, don’t you? What could possibly be going on in that skyscraper? What would compel it to resemble a Shewee? Are you kidding? Architecture, you’re drunk, as usual, on one gin and tonic.

Oh, I know there are those who say it doesn’t matter that all this towering sequestered air belongs to them and not to us, that ownership doesn’t alter the way the world looks. Really? REALLY? I’d rather be the us who built the South Bank, than the them who built that skein of phlegm, the Shard. That scaly talon, that giant middle finger presented to us all. I loathe its banality. The view from inside is better (no visible Shard), but it feels as if you’re inside some giant advert for double glazing. I loathe its monstrous, bullying scale. It’s Gulliver big. End-of-level-boss big. Its stupid anything-goes-now size mocks us.

And how I loathe the rhetorical guff, as empty as that “ultra-prime” floorspace at the top of the building itself. Its architect, Renzo Piano, calls it “a vertical city”? Really? It’s not Milton bloody Keynes, is it? A city must contain members of the public. That’s basic. Well, there aren’t many members of the public in the Shard, and they’re easily identifiable. They’re either there for drinks and dinner or they’re there for a meeting. They’ve either got a table reservation or they’re wearing a lanyard. Cities don’t have guest lists. The Shard is not a city. Where’s the school, the hospital, the weird newsagent’s that sells tinned pies? Where’s the social housing, the dodgy pub, the library? Come on.

Renzo Piano’s Shard, a ‘giant middle finger presented to us all’. Photograph: Mark Yeoman

Yet the orthodoxy prevails. London must attract investment. It mustn’t upset the capricious bankers and fickle wankers of capitalism, the lease-for-lifers, the buy-to-leavers. A low, grey sky of resignation about privatisation has settled over us. But if history and economics teach us anything, it’s that we have absolutely no idea what happens next.

On the current track, maybe life does become unbearable in the future, when the last remaining cubic centimetre of public space – a trembling pocket of air perhaps, in a cellar at the Emirates British Library – is finally acquired by a friend of King Charles III. At some point, there’ll be no more space left to squeeze and monetise. The city’s overlords will own everything. Qatari, Saudi, Russian, Indian, Chinese, some UK hedge funds named after Shakespearian characters – all air will be their air.

Architecture, you’re drunk, as usual, on one gin and tonic

In the future, the thin, sad air inside the last maglev night bus to Upminster, infused with metabolised alcohol, will be theirs. The dark, luxury air in the silent bedrooms of empty riverside apartments, their identical curving blocks clustered in threes and fours, grim and silent as gill slits, will be theirs. The once sacred air of St Paul’s Cathedral Spa and Pamperarium will be theirs.

Then – who knows? Maybe when London is pixellated into billions of stock-marketable units of sequestered air, boing! The world cracks and changes. Iceland acquires the north pole, discovers tons of diamonds and becomes the richest nation on earth. Ghana puts the first woman on Mars. Scientists announce they can convert rising sea levels into environmentally sustainable “brinergy”. The global petrochemical industry suffers a fatal prolapse. Its sheiks and warlords, the fawned-upon princes who once did as they wished – buying up most of Streatham in the morning, beheading someone for sorcery in the afternoon – well, they’re dust and shadow now. Maybe the global property market follows oil down the plughole. London’s last human inhabitants head north, their hovertransits stuffed with electronic belongings and omniplasma, to affordable housing, a temperate climate and a hopeful, collective future.

Or – who knows? Maybe the world economy goes tits up again, only this time we punish the rich instead of the poor. London’s part of a future that casts off the yoke of privatisation. Under new management. Ours. Imagine the London skyline repurposed as a collective landscape. A skyline where form no longer follows function, but where change of use might confer beauty.

Suppose those ridiculous blobs all over Waterloo’s sunset had different occupants. So a child points to the Shard and asks you what it’s for, and instead of trying to explain it’s half-full of dicks in haircuts “doing business”, you’re able to say it’s subsidised housing for key workers. Does it now magically become “architecturally beautiful”? Yes. YES.

And she points to the Gherkin and says: “What’s that?” and you say: “It’s a university.” What a beautiful world that would be. Maybe we can stop everything heading for a privatised wilderness. Let’s renationalise air.