Rather than demolishing Cumbernauld's brutalist town centre, we should learn from Patrick Geddes and employ radical surgery to give the megastructure a new lease of life, writes Rory Olcayto.

If you've seen Gregory's Girl, you'll know Cumbernauld has gentle, suburban charms. The romantic comedy dates from 1981, when the new town was still new. Landscape architect GP Youngman's meandering, green setting is to the fore, as Scottish teenagers aimlessly wander through it in the hope of a snog in the park.

But there's something missing: Geoffrey Copcutt's Brutalist Cumbernauld Town Centre, now threatened with demolition.

In truth, it does make an appearance – when two love birds meet for a date beneath the centre's Victorian clock (an import from Glasgow's demolished St Enoch railway station) – but that's all we see of the world-famous edifice.

Knock it the fuck down now, I was told on Twitter

It's odd because director Bill Forsyth celebrated Glasgow's modernism in his other Central Belt movie Comfort and Joy, in which the city's M8 motorway is as much a star as its lead actors. His refusal to show Cumbernauld's megastructure – with its pubs, clubs, bowling alleys, libraries and shops – feels deliberate.

Forsyth was one of Britain's most thoughtful directors and a passionate Scot too: his movies portrayed a Scotland with a wry, modern identity that sidestepped the contrasting images of No Mean City and Brigadoon that for years had defined how the rest of the world viewed the country and its people. In short, he knew what he was doing.

Perhaps Forsyth sensed the same dark energy that today sees locals calling for its demolition – "Knock it the fuck down now" I was told on Twitter, when I suggested it would be a mistake to do exactly that. "Then move here, you're in London. We have to live with it," they said.

I was shocked by what I found. Simply put, it was grim

I did actually move there – in 1973. When I was one, my parents, relocating to Scotland, chose Cumbernauld, excited by its vision of the future. We didn't stay long, but my dad's memory was positive, my mum's, less so.

In 2002 I found myself back there when GM+AD Architects was hired to revitalise the megastructure. I got to know the building quite well. I modelled it in 3D Studio and visited several times.

I was shocked by what I found. Simply put, it was grim. As Owen Hatherley notes in A New Kind of Bleak, "It's like a concrete shanty town, with . . . seemingly random cubic volumes "plugged in" . . . all in a drastic state, their concrete frames with brick infill looking half-finished, which alarmingly may have been intentional. One of these pods has a little doorway into a branch of William Hill, which is possibly the single bleakest thing I have seen in composing this book."

In truth Hatherley is complementary of the town, rightly – it's a nice place to live – especially its "glorious' northern suburbs, but there are echoes of Trainspotting's "worst toilet in Scotland" in his description of the megastructure that don't seem unfair.

The state of Cumbernauld Town Centre has resulted not from a failure of architectural design

Still, we shouldn't be knocking it down. If you've seen the average to very bad buildings that have, over the years, begun to crowd out Copcutt's building, you can be sure, if left to market forces, that whatever replaces it will be designed using Excel.

The state of Cumbernauld Town Centre has resulted not from a failure of architectural design, rather a failure of imagination: Copcutt's building was never fully realised and, like much of Scotland's modernist heritage, was mostly done on the cheap.

Copcutt's idea, however, was solid gold – and still gleams today. As he wrote in Architectural Design in May 1963: "In the extreme future, if particular central area functions decline (a formidable list of facilities that can be piped to the home can already be compiled) the centre could become a gigantic vending machine through which the motorized (sic) user drives to return revictualled, or more remotely, it could be turned over to industrial production."

He goes on to explain how this could be done, including "reserving sites for completely unknown and unforeseen uses with special buildings" alongside that would be linked to the centre.

Copcutt was from Yorkshire, but his sustainable vision for a future Cumbernauld chimes with the kind of intellectual ideas, practically applied, that gave shape to the Scottish Enlightenment. It chimes with one Enlightenment player in particular: the polymath Patrick Geddes.

One of the great thinkers – and do-ers – of the late 19th and early 20th centuries, Geddes is known today for his contributions to modern town planning, but he was also a biologist, an educator, a curator and a property speculator.

Geddes pioneered his "conservative surgery" urban planning approach

Among his many achievements, together with his English wife Anna Morton, Geddes refurbished tenements and courtyards located off the Royal Mile in Old Town Edinburgh, long since abandoned by the middle classes.

Here, Geddes pioneered his "conservative surgery" urban planning approach that removed the most dilapidated housing to improve sunlight and airflow.

Geddes' efforts had a major impact on the city's working class inhabitants, with infant mortality massively reduced. You might even say that without Geddes's interventions, Edinburgh's Old Town could well have been cleared away.

Geddes also created the Outlook Tower in the Old Town, a museum and urban study centre that fostered a local, national, and global "outlook" centred on people and place (yes, really, 120 years ago!). He was forever finding new uses for old buildings – with this last one especially apt for Cumbernauld, given the international acclaim Copcutt's megastructure garnered earlier in its life.

Cumbernauld's fate presents Scotland with a fundamental choice: it could "knock it the fuck down" – the favoured, contemporary mode of urban development for nigh on a century now and one the public has been gaslit into accepting. Or deploy the conservative – even radical – surgery, that Geddes showed was possible and Copcutt hoped would secure his building's future.

You'd think a nationalist-green coalition government, like the one installed at Holyrood, could spot the easy win here.

Rory Olcayto is a writer and critic at architecture studio Pollard Thomas Edwards. He was previously editor of The Architects' Journal and chief executive of Open City, the organisation behind Open House London. He studied architecture at the University of Strathclyde and previously worked in practice in Glasgow, Liege and Istanbul, and as a designer in the videogames industry.

The photo is by Ross Watson via Wikimedia Commons.