Ron Okey remembers it well, for all the time that has passed.
It's a secret history which has never been told - and would have stayed lost if not for an innocuous-seeming file accidentally placed with Archives NZ.
The file - now restricted for 100 years - details how his Palmerston North construction company edged out larger competitors to win the contract to build a top secret Ministry of Defence base out near the sand dunes of Manawatu's west coast.
The radio monitoring station at Tangimoana was to be an integral part of a global spying network. It cost the taxpayer about $1.4m in the end and became New Zealand's primary contribution to the Cold War.
It was 1980 and Okey had travelled to Wellington to sign an agreement at the Ministry of Defence to build the base at Tangimoana under the code name "Project Acorn".
He remembers his counterpart. "He had a pin-striped suit with a carnation in the buttonhole."
Along with the building contract came secrecy agreements - and it wasn't long before Okey learned just how seriously the Ministry of Defence took those agreements.
"We had some T-shirts done which I got my hand smacked for - Chip'n'Dale with a big bunch of acorns. We made them for the kids and all involved."
The T-shirts were a tongue-in-cheek coded reference to the Project Acorn building contract. Chip'n'Dale were the "secret squirrels". When the company's accountant wore one out jogging, it was seen by someone from Defence and set off alarm bells.
"We got told off in no uncertain terms." That was the end of the T-shirts.
The file now buried under Archives NZ's 100-year restriction gave rise to Okey's secret history of the building of Tangimoana. The Herald came across it while trawling through Archives NZ files on a range of subjects.
It's not the first time GCSB secrets have popped out this way. Journalist Helen Bain found a top secret GCSB report among the papers of former Prime Minister David Lange which detailed the countries - and organisations, including the United Nations - that New Zealand spied on.
It also recorded a threat from the US that if New Zealand went "No Nukes" - as we did - then we would become a target for intelligence-gathering.
These are our secret histories, and the Tangimoana file is just one story of a moment in the history of one of our most secretive organisations, the Government Communications Security Bureau.
The GCSB and its partner agency the NZ Security Intelligence Service rarely feature in Archives NZ's file. There's no doubt there's pride in the past - the Pipitea House headquarters has a small and fascinating museum of memorabilia.
And yet the publicly-known history is not glorious, as matters stand. The SIS is perpetually defined by the embarrassment suffered when one of its agents lost a briefcase which, when handed to a journalist, was found to contain a diary, meat pies and a pornographic magazine.
And the GCSB? The illegal spying on Kim Dotcom, exposed in 2012, is the bureau's greatest public marker.
The security services didn't much wish to talk about efforts to preserve their own history. Archives NZ ignored a request to talk about handling sensitive material.
A spokeswoman for the NZ Intelligence Community said the NZSIS had an archives programme "processing material as requested by the public, and as resources permit, other records judged to be of interest to the public".
There was no reference to the GCSB's records, although both it and the SIS are bound by the Public Records Act. "Records appraised as having long-term value are preserved and will ultimately be transferred to Archives New Zealand."
There are plans to "build a common approach and practice for the release of records" as the two agencies increasingly share services.
For the SAS, that was the same approach for many years. Sir Bruce Ferguson - former Chief of the Defence Force - knew he was crossing a line when he put Corporal Willie Apiata forward for the Victoria Cross.
It came with a price, says his former commander - "Willie was compromised".
Ferguson says the cost was clear to those serving alongside Apiata in the NZSAS. He remembers the reaction. "They said 'you can't do that'." The group was concerned about operational security.
In that case, he says the greater good was important - recognition for Apiata's bravery, for the role the SAS played and recognition for the wider NZ Defence Force followed the award.
It was followed by the official history of the secretive unit - NZSAS: The First Fifty Years - written by lawyer and historian Ron Crosby.
It's an exacting accounting of the unit's history, peppered with interviews from SAS members and details of actual operations.
To write the book, Crosby had access to SAS members for extended periods and reviewed documentation which was patchy - in parts, he believed, because of the unit's drive to secrecy.
It was reviewed by senior NZDF commanders - and for all the secrets it spills, for all the operations it details, very little was removed. And no evidence has emerged since that the SAS are imperilled in the job they do.
The book now serves to plug a 50-year-sized hole in history.
When Ferguson left NZDF, he become director of the Government Communications Security Bureau and found it even more secretive. "When I was CDF (Chief of Defence Force), I made sure praise was given when it was due," says Ferguson. "You couldn't do that with the GCSB.
"Like the SAS, you have to be very careful not to tell the opposition too much of what you do. A little bit can be a little too much."
Even the smallest hints of how secret units operate can provide valuable information to opposing forces.
"The GCSB, like the SAS, is very much of the 'just don't bother saying anything because that's the easiest way' school."
In the case of the technology-based GCSB, publication of outdated technology gives opponents the opportunity to plot a path to the present day in terms of capability.
"It's far easier in that grey area to just shut up. That is always going to compromise getting history out." And of the people in those secretive services? "They would say, 'so what?' The job is far more important."
Ferguson maintains "an innocent piece of information, even a little bit" has the potential to create unacceptable risk. The secret services work in areas of life and death - disclosure has the potential to kill.
"I know inside the bureau it was sometimes hard for people. They were doing great things but you couldn't acknowledge it, not even to their families."
He agrees there is a strong public desire to know. "The want of people to know is great. But if that compromises even one life? And that could quite easily happen."
Rubbish, says investigative journalist Nicky Hager. Why don't we benchmark our level of disclosure at that of our lead intelligence partner, the United States?
"If we followed the Americans, people would know light years more than they do now."
For example, search for the "official history of the Central Intelligence Agency". It has a 340-page collection of material from the disastrous Bay of Pigs assault.
The problem is the so-called "mosaic theory", says Hager. "Security people believe - and it's belief, not knowledge - that every single piece of knowledge handed out will add on to another one and have consequences for the security of the country.
"We have counter-evidence that every time there are leaks out of these agencies, the sky doesn't fall down.
"Experience tells us that the place where they draw the line is miles away from anything to do with security."
Hager knows this well. He detailed the operations of Tangimoana - and the work of the GCSB - in his 1996 book Secret Power. It was a global scoop, revealing the existence of the signals-intelligence network called Echelon and New Zealand's role in it.
"I know there was no talk about irreparable damage - and this was a book that had diagrams of secret facilities, what their jobs were, what their names were.
"The main comments were 'why wasn't my name in the book?' These poor workers had maybe gone for decades giving their lives to a secret agency. They couldn't even tell their children or partners what they do."
Looking back on the Tangimoana project, construction boss Okey reckons the plans are still around the office somewhere.
"They were so uptight about security, but they never collected the drawings. I thought it was a bit funny at the time."
It was a complicated project in a remote area. There was no water, no electricity, and not even road access to the Landcorp farm where the base was to be built. It was so remote there was just one shared "party line" for anyone wanting to telephone into or out of the base.
Okey says it would create the hilarious scene of workers chatting on the phone about "their jam recipe" with the military liaison person waiting to call headquarters. "It was quite funny. It could only happen in New Zealand."
The locals at Tangimoana had their own rumour mill - "they thought we were building a rocket base for the Americans.
"All I know about it is there were a lot of boffins out there and they did their boffining and we did our building."
And still, the only stories that are told are those that fall out by accident.