It remains the worst road crash in New Zealand.
Those first on the scene that day spoke to the Herald. One described the bus as "a splintered and tangled mass of wooden wreckage".
Others spoke of scrambling down that precarious hill to help survivors.
A farmer whose homestead overlooked the gully where the bus came to stop heard the crash, saw the dust rising.
"I thought at first it was a truck over the edge ... when we got down the hill we were shocked. It was a nightmare scene, just a mass of broken bodies.
"One boy was hysterical and kept calling for his brother while we were getting him out. I don't know whether his brother was one of the lucky ones."
The farmer's son also witnessed the horrific scene, recalling: "It was just a tangle of bodies when we got there. People were moaning with pain and trying to haul themselves out of the wreckage."
"I have never seen anything like it," said a policeman.
A public inquiry was held in April.
It was the first time New Zealanders would hear bus driver Harold Parker tell his story. As he headed from Waitangi to Auckland, the bus seemed fine. He pulled in near Ruakaka for a lunch break and then again on the Auckland side of Pilbrow Hill - part of the Brynderwyns.
Soon after, disaster struck.
"My brakes have gone," he told his passengers.
"When I did apply the foot brake the pedal went straight to the floor. I tried to change from third gear into second but failed ... at the same time I applied the handbrake and to get more leverage I stood up.
"I was able to drive around at least two bends with one hand on the wheel while the other was pulling on the handbrake ... I have no idea what speed the bus was travelling at," he told the inquiry.
"I knew that if I did run the bus into the side of the bank, the top of the bus would splinter and the sides would fall away. I was conscious also of the steep drop on the other side. I knew I was nearly at the bottom of the hill and if I could make one more bend I would be on a straight road."
As the bus was hurtling down the road, Mr Parker could see his passengers in the rearview mirror. Some had left their seats and were standing, encouraging him.
"Stick to it, you'll make it driver," one called out to him.
"I was attempting to drive around the bend, the speed was too much and the bus went over the bank."
Seconds later, almost half of his passengers were dead. Survivor Tunatapa Kukatai spoke of the passengers' terror as the bus plunged down the hill.
"There was a happy part on the bus, all the younger ones were singing as we started down the hill. There was no panic and people kept to their seats when everyone realised that something was wrong. The older people began to pray out loud. Someone said 'we will be all right' ... I was one of the very lucky ones."
'The unspeakable was in his eyes'
Don Hutchinson was just 13 years old when his uncle Tamaio Paiki turned up at his family's home in Takapuna. But he remembers it vividly.
"Uncle Tom came unannounced to our house in Takapuna, sombre and shirtless. He'd been returning from Waitangi in a bus full of local-area Maori when, as they descended the Brynderwyn Hill, the bus in front suddenly picked up speed, careened around a corner then left the road and plunged down a steep hill into a stream. The brakes had failed," Mr Hutchinson told the Herald.
"Tamaio and others quickly scrambled down through broken trees and ferns to a scene he described as 'pure carnage'. When he got to our house later that night his white shirt was just a blood-stained ball under his arm. He'd forgotten he was carrying it till Mum offered to wash it.
"In his gravelly, soft-spoken voice he slowly related the details of the crash and a summary of the rescue attempt. Though not one to speak of gory details, you could see the unspeakable in his eyes."
Mr Paiki died in 1984.
"Do I consider his actions heroic? Of course I do. Anyone who plunges without thinking down a hillside to extricate the living and the dead from a crumpled vehicle deserves respect. But he was not alone and I doubt any of the rescuers did it for personal glory," Mr Hutchinson said.
"They simply did what any decent person would do in the 1960s - and hopefully today.
In any case, he was already a hero in my eyes, but a modest one who would never have allowed such talk."
Mr Hutchinson often thinks about the crash.
"Although we didn't know any of the victims, somehow they seemed closer to us because of him. The name Brynderwyn and Paiki's blood-stained shirt are forever seared into my memory."
The victims
Dead: 15
Beryl Abraham-Paenganui
Dolly Bidois
Miriama Nathan
Steve Nathan
Emma Nielson
Ropata Pouaka
Ngarotokurua Molly Povey
Colleen Margaret Sheffield
Peter Tapene
Maringi Kaa Taratu
Eriapa Poata Uruamo
Karaka Wiapo
Celia Kidwell
Levia Kidwell
Ben Kingi
Injured: 21
Bus driver Harold Parker, 46, lacerations
Lewis Nathan, 16, back injury and lacerations
Valma Tapene, 13, chest injuries
Annie Tapene, head injuries and fractured arm
Lily Smith, 52, head lacerations and chest injuries
Wikitoria Rota, 30, shoulder injury
Byron Kidwell, 13, left leg compound fracture
Pute Kidwell, 12, chest injuries
Rangi Clark, 51, chest and spinal injuries
Livia Edwards, 13, abdominal injuries
Nuki Broughton, 55, chest injuries
Pirangi Nathan, 15, facial lacerations and chest injuries
Tunatapa Kukutai, 26, back injuries and facial lacerations
Anette Houpapa, 15, fractured spine
Waru Beckett, 40, chest injuries and shoulder fracture
Susan Tane, 22, chest injuries, broken back
Mrs B. Neilson, back injuries
Ruby Noda, 58, fractured leg and back injuries
Mrs E. Moore, multiple fractures
John Parata, 31, arm lacerations
Elizabeth Povey, 30, neck injuries.
Read more:
Brynderwyn tragedy: A tale of two families
Don Milne: Horrendous sight of 14 bodies laid out in a line