Retired Judge John Bisphan was Cadenhead's closest friend and spoke to the Herald today about his loss.
"It was an awful shock," he said.
"It was unexpected.
"They were on holiday and he just seemed to get some unexpected illness."
Cadenhead's wife was with him in hospital when he died.
"I've known him for 70 years. He was just my closest mate," he said.
The pair met at primary school in Christchurch and attended Christchurch Boys' High School.
They went on to study law and stayed good friends.
Cadenhead worked as a lawyer - specialising in injury claims and criminal defence - before he was appointed as a magistrate in 1977.
He went on to be appointed a District Court Judge in 1984 and relocated to Auckland where he served in the role until his retirement in 2004.
Bisphan also became a judge, but remained in Christchurch.
Over the years the pair holidayed together with their families, often in Hawaii.
Cadenhead retired about seven years ago and Bisphan said he was enjoying a quieter life.
One of his biggest achievements outside the courtroom was completing his doctorate at the University of Auckland.
He was the first judge to do so.
"He was very determined and I think that's what underpinned his success," Bisphan said.
"With his doctorate, and on the bench and in his legal practice."
Despite that success he remained humble and valued his friends and family.
"He was just an ordinary guy, like the rest of us," said Bisphan.
Cadenhead's funeral will be held next Friday 15 September in Remuera.
News of his death shocked former colleagues and friends.
Judge Fred McElrea told the Herald he received a call from Cadenhead's son David who was in Honolulu with Diana, soon after the 80-year-old died.
"It was a sudden blow, it came out of the blue," he said.
He was also a good friend of Cadenhead and spoke at his retirement dinner in 2004.
"He was brilliant," McElrea said.
"He was a real character - a delightful character and he will be remembered by a lot of people as exactly that.
"He was a humble man, but very wise and very able and quite astute.
"He was always there to help other people, judges and counsel.
"He also did a lot of other things too, apart from sitting as a judge."
Alongside his doctorate, Cadenhead spent his sabbatical studying at Cambridge University in England and Stamford University in the US.
He lectured in civil proceedings and authored the district court practice guide for nine years.
Cadenhead was also the district court representative on the Legal Research Foundation Council for about five years, and spent a similar period on the New Zealand Council of Legal Education.
"Part of his philosophy was that a good judge was anonymous - in other words you avoid the limelight or any grandstanding," McElrea said.
He would always remember the advice his friend gave him.
Retired Judge Roy Wade also paid tribute to his colleague.
Wade was a lawyer when he first encountered then-Judge Cadenhead.
"I first appeared before John Cadenhead very shortly after I arrived in 1994 when a case I was prosecuting had to be adjourned," he recalled.
"Although I wrote the new date on the file, I completely forgot to cross-reference it in my diary so did not attend at the scheduled time.
"Eventually the court tracked me down but as there were no cellphones then, I was well over an hour late by the time I reached his courtroom.
"I was so profuse in my apologies to him, my opponent and his client that John Cadenhead not only instantly forgave me but insisted the court was at least partly to blame for not having sent me a reminder.
"Now that's what you call a real gentleman."
