An Auckland man who after 27 years in a relationship was left only with his partner's ashes has been awarded $300,000 by a High Court judge.

The estate of Steven Moon's now deceased partner, Mary Doyle, was ordered by Justice Grant Powell to pay the sum after it was declared the two were in a de facto relationship.

Doyle had repeatedly listed herself as single on formal documents.

Doyle died in January 2017 following a long battle with cancer, leaving her Fairview Rd house to her brother Patrick.

In a note to Moon following her death Doyle wrote: "I'm leaving you the most precious thing:- me. (even though it's in a box)."

A just-released High Court decisions says Moon, 62, was "upset and felt used" when he read her will and found he would not get her whole estate as expected, instead only her ashes.

"I do feel that in death Mary should have put me first as I put her first in life. I feel betrayed by her.

"It was as if I was nobody in her life. I had spent nearly every day with her for 27 years, except for two and a half weeks when I was in hospital and some short trips to the South Island," he told the High Court at Auckland.

The pair did not live together. Moon lived next to his mother in Torbay and Doyle lived at the Fairview Avenue address.

There was evidence that the couple looked for a property together in the 1990s but it was "ultimately not pursued as both found their respective properties suited their different needs".

They would text daily and Moon would often cook dinner for Doyle at her residence after getting her medication and picking up groceries.

"I helped Mary get changed for bed and would kiss her goodnight before going to my house," Moon said.

He claimed for her whole estate which was challenged by Patrick who claimed she and Moon were not in a de facto relationship.

Patrick said Doyle had always described herself as single and when asked by the Public Trust if Moon was her partner when she was composing her will she said he was a companion only, the decision says.

Patrick acknowledged the two were in a "long and close relationship, the evidence supports a finding that it was one of friend not husband", but said the relationship did not meet the criteria of a de facto relationship.

Maxine Blake, a childhood friend of Doyle, said she never thought Moon was just a platonic friend.

"I was not living with Mary, but I always understood that they had a romantic
and sexual relationship."

Justice Powell said despite Doyle describing Moon as a "friend", the pair were in a de facto relationship.

"Ultimately the picture that emerges is of two quite private people who formed a relationship that worked for them despite very considerable difficulties arising from Mary's medical conditions," Powell said.

The $300,000 payment from the estate would almost certainly require the sale of Doyle's house which was meant for her brother.

Powell ordered the costs of Moon and Patrick would be met by the estate.