The death of 63-year-old Nelson tramper John Hannah was an accident and not the result of any lapse in preparation or management by the expedition group he was with, coroner Carla na Nagara said.
Mr Hannah, a pioneering figure in the New Zealand aquaculture industry, died on December 9, 2011, after falling during a climb in Kahurangi National Park.
He was negotiating difficult terrain with former Tasman District Council chief executive Bob Dickinson and Nelson Symphony Orchestra chairman Richard Wells in the Adelaide Tarn area of the park when he fell about 20 metres to his death.
A fourth member of their party, Dr David Low, had slipped and broken his ankle earlier in the day. He had been airflifted from near Lonely Lake by the Nelson Marlborough rescue helicopter.
Ms na Nagara said the group was on the third day of a tramping expedition when the accident happened. They were all fit and experienced trampers who had tramped together extensively over 20 years.
The hike they planned that day was from Lonely Lake Hut to the Adelaide Tarn, over a route that was new to all of them. They expected it to be the longest and toughest day of their expedition, Ms na Nagara said.
About mid morning Dr Low injured his ankle. The emergency locator beacon carried by Mr Hannah was activated and about an hour later the rescue helicopter flew Dr Low out. The other three carried on.
After a lunch stop at Anatoki River they followed the valley up to the headwaters for a climb up the Adelaide Tarn.
At 6.15pm Mr Dickinson suggested they break for tea but Mr Hannah and Mr Wells were keen to carry on.
At the end of the valley the men found "two good cairns" on a face which they went straight up and over. They ended up in a steep chute with a rock in the middle, which Mr Dickinson and Mr Wells scrambled up. Mr Dickinson did not think it steep enough to warrant throwing down the light rope they had with them.
As Mr Hannah began the climb up the chute, he was suddenly heard to cry out and then a rumbling noise was heard. Mr Dickinson did not see him initially, but he appeared as he rolled and slid further down the chute.
Mr Dickinson and Mr Wells climbed down to Mr Hannah to find him bleeding from the head and non-responsive.
For the second time that day they activated their emergency locator beacon and Mr Dickinson and Mr Wells were airlifted out that night. The rescue helicopter crew confirmed Mr Hannah had died, but conditions at the time prevented them taking out his body and he was recovered the next day.
Ms na Nagara said an autopsy confirmed he died as a result of a severe head injury. There was also evidence of a spinal injury.
"As Mr Hannah's fall was unwitnessed it is not possible to be definitive as to why it occurred," she said.
It was possible he simply lost his hand grip, or footing, or was over-balanced when something caught his pack, Ms na Nagara said.
Mountain guide Geoff Wayatt, who was asked to provide an opinion on the circumstances of the fall, noted the accident happened at the end of a long and arduous day and that the men were separated at the time of the fall.
Mr Wayatt noted that while there are some good safety reasons for maintaining moderate separation on steep, loose terrain, there are equally sound reasons for staying close together to allow good communication and to provide mutual support.
The coroner was satisfied the fall was an accident and said the point was to raise awareness of the risks in the environment the men were in, in the hope it would reduce the chance of anything similar happening again.
Mr Dickinson told the Nelson Mail yesterday he thought the report was "very fair" and helped confirm what they thought had happened.