Rudyy was living with Collie and her son Andrew in a clifftop mansion in Murrays Bay. She went for her daily walk on the beach at Rothesay Bay at 12.45pm on July 2, 2011, the coroner's report said.
An hour later, Andrew and his grandmother found that Rudyy's Yorkshire terrier, Saska, had returned home.
They immediately sensed something was wrong and rushed to the beach, only to find emergency services had already arrived.
Police launched an inquiry that looked "carefully" at whether anyone might have been responsible for Rudyy's death, Coroner Ryan said.
However, they found no evidence of anything suspicious, "either directly or indirectly".
The inquiry report said Collie was at work on the morning of July 2, and did not return home until approximately 2pm.
Witnesses vouched for the Atlas Concrete director, and his cellphone records also verified his location.
"The chance of a member of the public observing an attack on Rudyy would have been very high, and therefore it is most unlikely that a person intent on killing her would choose that location," Ryan said.
Engineering consultants Tonkin & Taylor, in a report commissioned by the Auckland Council, said they found three locations where minor rockfalls had occurred.
Rudyy's body was found 7m from the base of the cliff, well within the "fall zone" identified by the report.
The coroner ruled that she died of head and chest injuries caused by falling rocks. Auckland Council had since put up more signs to warn of rockfalls, Ryan said.
The criminal history to which the coroner referred was Collie's 1993 convictions for violent sex attacks on eight women.
Jane Furlong - whose remains were found at Port Waikato in May last year - had been due to testify against him when she disappeared in May of that year.
Police have reopened their investigation into Furlong's murder, and last month they interviewed her former boyfriend, Danny Norsworthy.
Since his wife's death, Collie has put his mansion on the market and moved to another home he owns in Hauraki, also on the North Shore.
The coroner's report referred to anecdotal evidence of difficulties in the marriage, but yesterday, Collie said his relationship with his wife had been "fine".
"Every marriage has its ups and downs but we were getting along fine and always have done," the millionaire told the Herald on Sunday.
"There wasn't relationship difficulties at all. I don't want you writing anything in the paper that I was having difficulties with my wife, when we were getting along well.
"They have got no right to say that we were having difficulties. [The police] never asked me that question.
"Someone has stuck their spoke in and said some untruths."
Collie said he was not interviewed as a suspect. "I was at work. There was never any indication from the police that I was a suspect.
"The f***ing cliff came down and a rock hit her on the head. The police were more than helpful. They asked everyone in the family, 'Where were you?"'
Collie added that his family wanted to be left alone. "The whole family has had enough. My grandkids, my kids. I was not a suspect in my wife's death."
