The Supreme Court's ruling in the Tate Modern privacy case is part of a depressing trend towards London's views becoming increasingly controlled and commoditised, writes Helen Barrett.

Absolute Beginners, Colin MacInnes's 1959 novel about London on the brink of social revolution, opens in "a glass garden under the top roof of a department store". Its narrator, a sharp, working-class teenage hustler, stands and surveys "the glorious panorama" of the postwar city under construction.

The store could be Harvey Nichols, or the former Derry & Toms on Kensington High Street. It doesn't matter. The point is perspective: from his vantage point, MacInnes's hero sees London's infinite possibilities laid out before him, all for the price of a coffee.

Last week, Londoners lost one of the best ways to take in their "glorious panorama".

Tate's platform could now close to placate a handful of wealthy people

The Supreme Court's ruling in a privacy case over Tate Modern's 360-degree viewing deck could mark the beginning of the end for one of London's greatest joys: escaping the noise of the street to gaze at the spectacle from a viewing platform that is free, welcoming and open to anyone at any reasonable time.

Owners of flats in Neo Bankside, RSHP's luxury glass-walled block next to the UK's most-visited art gallery, had claimed that "hundreds of thousands" of people were gawking into their homes every year. The UK's highest court ruled by a majority in their favour, agreeing the platform was a "legal nuisance" and not a "normal" use of land.

The message seems to be that private assets are to be fortified at all costs, even at the expense of everyone else. Tate's platform could now close to placate a handful of wealthy people who will likely get London's exhilarating vista to themselves, but the repercussions may go further than that. The rest of us are left facing the creeping privatisation of 360-degree views.

"It might start to reflect in developments where privacy overrules public good and public benefit," says Make Architects founder Ken Shuttleworth, who, while at Foster + Partners, incorporated a viewing deck into Southwark's City Hall. That deck, which opened not far from Tate Modern in 2002, was occasionally open to the public (it, too, has closed, with the building currently shuttered).

"The danger is that no-one is going to want to [include a viewing platform]," says Shuttleworth. "A lot of planners try to do the right thing, encouraging buildings to have a public focus with free roof access. But if developers can argue that the guy over the road might close it down, they won't do it. Who wants a legal battle?"

"London has changed quickly in becoming a vertical city in a way that, historically, it was not," adds urbanist professor Rowland Atkinson of Sheffield University, and author of Alpha City: How London was Captured by the Super Rich. "But that vertical landscape is an exclusive one. It does not invite a diverse demographic."

"If disconnection is what money buys, that creates an exclusive city."

There is no shortage of hyper-monetised vistas for those who can pay

London's numerous private viewing decks suggest he is right. There is no shortage of hyper-monetised vistas for those who can pay to get in.

Most recent is Lift 109 at Battersea Power Station – where visitors ascend one of its two river-facing towers to enjoy the panorama from a small glass box for a limited number of minutes. Spectacular, but at £50.40 for a family of four, far from egalitarian.

The Shard's view is even more heavily commodified: the privilege of gazing at the vista from London's tallest building costs about £30. Absolute exclusivity can be bought: the Shard's "proposal package" – perfect for St Valentine's Day – costs nearly £800.

Foster + Partners' Tulip, designed for Brazilian billionaire Jacob Safra, may have been ultimately rejected by the government, but stands as yet more evidence of the trend towards commodifying London's views.

Some tall buildings offer free sky gardens and viewing galleries as fringe benefits. But they erect other barriers.

The Sky Garden in the Fenchurch Street Building, "London's highest public garden", is particularly sanitised. It encourages pre-booking, demands airport-style x-ray scans and issues a dreary list of regulations. You can only stay for an hour.

Other vistas that claim to be open to everyone are almost in hiding. You could walk through One New Change, the glitzy shopping mall next to St Paul's Cathedral, without knowing that lifts will take you to a free, expansive roof terrace, so little is advertised about its existence. The view is sensational, despite the security guards.

Just as reticent is the free public rooftop garden at the Post Building on Museum Street (a small sign on a door at street level). Barely anyone seems to know The Garden at 120, also on Fenchurch Street, open to the public until 9pm on weekday summer evenings (with the inevitable checks and rules), judging by its deserted terraces.

The joy of Tate Modern's platform was its greater generosity and its lack of sterility

Some developers work viewing platforms into their public benefit offering in the hope of getting planning permission over the line. One of the most dizzying, if approved, will be the 63-storey 55 Bishopsgate, which developers are proposing to top with a Sky Garden-style "unique, triple-height space free to access… one of the highest accessible roof spaces in London". It promises curated public events throughout the year.

Promises can be broken, though. Berkeley Group's 50-storey One Blackfriars, designed by SimpsonHaugh, was set to feature a "public sky deck" when it gained planning permission in 2009, as compensation for a lack of affordable housing. That was later downgraded to a "managed viewing lounge" and is now a residents-only "executive lounge".

Developer-led viewing platforms are arguably better than nothing at all, of course, and there are still a few department-store vistas available for the price of a coffee, though Derry & Toms has long been converted into private offices.

But the joy of Tate Modern's platform was its greater generosity and its lack of sterility. Not only was it free, there were no time restrictions; no booking slots. You could take in the glorious panorama for as long as you liked. Unlike the glass towers, visitors could scan south London, the perennial poor relation, as well as north, west and east.

"Open access has become critical," says Atkinson. "Public services and the spaces and places that don't cost are the glue of the community. So this decision brings real concerns about others deciding they have the money – and feel emboldened – to contest that."

Londoners have come to see vantage points as their birthright – part of the great spectacle since at least 1671, when Christopher Wren and Robert Hooke's Monument to commemorate the Great Fire was built "the better to preserve the memory of this dreadful visitation".

Monument offered a view of the rebuilding and reimagining of the city, just as MacInnes's hero enjoyed 300 years later. You can still climb it for about £5 – though the view has largely been obliterated by skyscrapers.

Helen Barrett is a journalist based in London who has written for The Daily Telegraph, The Spectator and the Financial Times, where she previously edited the FT House & Home section. She is also a director of the London Modern festival.

The photo is by Jim Stephenson.