Architect Justin Leadbetter amid the Cranmer Courts rubble. Photograph: Rebecca Macfie

For a brief 10 minutes or so Justin Leadbetter managed to do what advocacy, placards and endless public meetings have failed to do in Christchurch. He stood – sat, actually – between the claws of a large orange excavator and the magnificent 136-year-old Cranmer Courts building, and stopped the destruction.

It was a short, polite act of defiance by an architect angry enough about the mincing of the city’s heritage and the squandering of crafted building materials to risk arrest. The police were quickly there, ushering him off the pile of rubble on which he’d perched himself, and sent him off with a warning.

The sad fact is that for those who grieve for Christchurch’s diminishing architectural treasures, direct action may be the only option left. A couple of hundreds of metres away from where the Jurgens excavator was making history of the Cranmer Courts, the High Court was hearing a desperate last-ditch case brought by former MPs Jim Anderton and Philip Burdon, who have discovered an obscure piece of legislation that just might save the Christ Church Cathedral from the wrecking ball. We will know in a few weeks if they have been successful.

In the case of Cranmer Courts – an imposing Gothic Revival building built in 1876 to house Christchurch Normal School, and redeveloped as apartments in the 1980s – a small but distressed group of protesters assembled early on Thursday morning after hearing word the evening before that demolition was starting at 9am.

But the cries of “shame” and “cultural vandalism” that went up as the engine cranked into life were futile, and everyone knew it. There was, mostly, just a sense of tired disbelief that no-one had been able to mount a successful defence for a building that has dominated its corner of the city and shaped the urban landscape for more than 13 decades – a building listed as Category 1 on the Historic Places register, equal in importance to Parliament Buildings and the Auckland War Memorial Museum.

Serious effort was made to save Cranmer Courts, but the odds were stacked against it. Yes, 10,000 earthquakes had left the building with extensive damage. But the owners had carefully and diligently boarded it up to protect it from the weather, and fenced it off from its busy Montreal-Kilmore St corner so that it posed no danger to passing cars and cyclists. Nevertheless, the Canterbury Earthquake Recovery Authority several months ago slapped on a Section 38 notice – make it safe, or demolish it – and the owners didn’t have the means to come up with a plan that would satisfy CERA. Section 38 notices suspend all the normal protections for listed heritage buildings – demolition can proceed without the requirement for resource consents or public consultation.

The demolition crews were already at work a month ago when a conditional offer came through from an Australian buyer who wanted to save the historical façade and redevelop the site. CERA agreed to put a hold on the demolition while the owners negotiated a deal (mind you, it also charged them thousands of dollars a day for the cost of suspending the demolition contract).

But in the end the potential buyer couldn’t make it stack up. The key stumbling block was CERA’s Section 38 order, which hang like a sword of Damocles over any potential deal. The risk for the buyer was that he could buy the property, spend large sums coming up with a make-safe plan, and still not satisfy the all-powerful CERA.

The deal fell over last Friday. CERA was informed on Monday. And by 9am Thursday the place was beginning to be reduced to a pile of mulch.

Could anything more have been done? The owners – 31 apartment owners, tied together as a body corporate – have received their insurance payout on the building but they need to be able to sell the land to move on. Many of them are elderly, are displaced from their homes, and don’t have deep enough pockets to rescue the building.

CERA, as one person close to the negotiations over the building told me, is not entirely to blame – but nor did it help. Its powers are sweeping and, from the moment the Section 38 was issued, any opportunity for heritage advocates to be heard was lost. And, despite having duly drafted up a heritage recovery programme for the city, as an organisation it is – at best – agnostic about the city’s historic fabric. Gerry Brownlee set the tone early on – remember the order to get the “old dungers” down?

According to heritage advocate Lorraine North, over 50% of Christchurch’s listed heritage buildings in the central city have already been demolished; in many cases the demolition has been facilitated by CERA’s Section 38 notices.

And it will keep on happening.

Ian Lochhead, an expert in the Gothic Revival architecture for which Christchurch used to be famous, told me this morning while we waited for the excavator to land the first, inevitable blow on Cranmer Courts, that “some of the 20th century’s most brutal regimes did more to save their country’s heritage than CERA and the National Government have done in Christchurch. Stalin did more in Soviet Russia to recover heritage after the second world war than we are seeing here.”

If CERA followed its own statements on heritage, “this would not be happening. But those statements are completely hollow. This is demonstrating just how hollow.”