Two days later they set off for Homer Saddle, intending to stay at a location known as Camp Dog for two nights before returning.
On the first night Mr Sedon and Mr Evrard stayed in a tent while Mr Whimp "made do" with a tent fly.
After dinner it started raining hard so they went to bed.
"The following morning it was still raining. All of them were very wet," Coroner Crerar said.
The trio decided to return to their car a day early, but about an hour into the walk Mr Whimp fell.
"The terrain near Camp Dog was described as steep and exposed and the slabs of rock being described as wet and running with water."
Mr Whimp was following Mr Evrard when he stepped down onto an area of mud and slipped.
"The terrain where Athol slipped was the sort of terrain any Joe Bloggs could walk along no problem except that it was exposed," Mr Sedon told Coroner Crerar.
Mr Evrard said he turned around to see Mr Whimp tumbling off the side of the mountain.
The pair used ropes to try and get to Mr Whimp but they could not see him and called emergency services.
Mr Whimp was described as athletic and fit, wearing appropriate clothing for the climb and had suitable boots for the terrain.
A report by experienced mountain guide Geoffrey Wayatt said he was satisfied the trio had adequately rested and eaten before the walk.
"The exact reason for the slip could be from a single or multitude of factors, one being a momentary loss of concentration."
He doubted whether wearing a helmet would have resulted in a different outcome.
Coroner Crerar recommended mountain information services continue to provide information on the hazardous nature of New Zealand's mountain routes, particularly in wet conditions.
He also recommended that climbers wearing heavy packs paid attention to their safety and ensured their footwear was appropriate, and that individuals considered their security by using two- or three-point contact when scrambling.
