Sydney GPO has been sold in a secretive deal for $150 million. Credit:Wolter Peeters Flashback: The year is 1993. Location: the ornate Finance Room in Town Hall. Meeting of the developer-heavy Central Sydney Planning Committee, of which I am a member. Several suits from the newly corporatised Australia Post are presenting their proposal to stuff a high-rise hotel into the guts of the GPO. "Just treat us like any other developer," they say. And it strikes me like a freight train that they don't mean "no special favours because we're government". They mean, "we're far enough from government to pursue profit single-mindedly and still part of it enough to be immune to your rules. This is going to be BIG and you're powerless to stop us." That was the beginning, for the GPO. Now, the endgame is played out. Our finest and most loved building is no longer ours. The GPO, built of finest Pyrmont yellow block between 1866 and 1891, is the career highpoint of Colonial Architect James Barnet. Nothing like it can ever, or will ever, be built again. Widening the narrow St Martin's Lane to form what is still our main public piazza, the GPO was a slow build because it spans the Tank Stream that still runs beneath. It was, and is, Sydney's heart.

The exterior of 1 Martin Place, Sydney's GPO. Built between 1866 and 1891, it is the career highpoint of Colonial Architect James Barnet. Credit:Wolter Peeters The fine Italianate façade, the gravitas of the step-fronted street colonnades, the vaulted sandstone and granite arcades, the soaring campanile with its pretty bell cupola and alabaster clocks and the black-and-white tessellated granite floors – all this not only established the GPO symbolically as New South Wales' most important building but trumpeted a new confidence in project New South Wales. The carvings alone are hand-worked allegorical reliefs by immigrant sculptor Tomaso Sani. Despite being sufficiently controversial at the time to end Barnet's career, they were later hailed in the Legislative Assembly (1890) as "the beginnings of art in Australia". The controversy centred on the GPO's Pitt Street façade. Barnet was determined to decorate his building with allegorical narrative peopled by men and women in contemporary daywear. Flouting classical norms, thus, the Pitt Street sculptures were seen as ugly caricatures. Now, we admire and love their voluptuous realism, as well as the care and industry of their making. There is also the dim recognition that, even if we wanted to, and could afford it, we no longer have the skill. Truly, this is a lost art. And we flog it? Seriously? The GPO is not alone. Sydney's grand sandstone heart comprises a clutch of fine buildings whose courage and confidence tell us who we are as a city, and a nation. History gives place meaning. It tethers us against the void. These buildings represent our best, most civic, most grounded selves. They anchor us, and the GPO anchors them.

Yet, one by one, these buildings are going. Lands Building – gone. Education Building – gone. Land Titles – gone. Now the GPO. Gone, forever. Are we mad? These are not mere assets. History is all we have. Says NSW National Trust president, architect Clive Lucas, "a nation that forgets its history is a nation that has no future". I know what you'll say. We'll still have the buildings. Uses change, owners change, but bricks and mortar persist. Will they, though? Are you sure? And is the fabric by itself enough? We have this idea that "heritage listed" means something solid. It's a dangerous furphy. Certainly, at state level, heritage "listing" implies no level of mandatory protection. (The community's triumph over the Sirius may be short-lived, for this reason. Even if by some miracle the Environment Minister Gabrielle Upton decides to list the Sirius, she has only to declare its redevelopment "state significant" for the Heritage Act, and most other environmental protections, to be turned off. Hundreds of quite insignificant buildings, from schools to universities to office towers, are routinely declared state significant with this in mind. So we're back to feudalism: rules for the small guys and no rules for anyone big enough to attract the minster's favour.) At Commonwealth level, it's even sillier. Australia Post says it will seek National Heritage listing for the building it has just sold. Even if it were to eventuate, however, this would co-list it with the Greater Blue Mountains (where Western Sydney University researchers recently found some of the world's most toxic water pollution, dumped legally by Centennial Coal's underground mine) and the Great Barrier Reef, now mostly dead.

So how much faith should we put in this list's capacity to protect the building now? Or in the promises of owner Ms Lay See Shaw, CEO of the Far East Organisation, to be "guided by all relevant state and federal heritage laws and regulations". Loading Not a lot, perhaps. But the shameful truth is that the building's new owners could hardly be worse – less caring or altruistic – than the governments to whom we look for its, and our, protection. The GPO's 300-page heritage plan is considered top secret. The one thing we know is that it strongly opposed the sale. I rest my case.