Warning: This story and related coverage of the trial contains graphic and sexual details that may be distressing to some readers

A woman who lived with Grace Millane's killer says he was so scary one of their flatmates took a knife to bed with her for protection.

Photo: RNZ / YouTube

The woman, who RNZ has agreed not to name, says she "feels a huge sense of relief" after a jury yesterday found him guilty of murdering British backpacker Ms Millane, who he met on Tinder.

The woman, along with two other female flatmates, shared a Greenlane house with the man in 2016, after he responded to their Facebook post on an Auckland flatmates group.

But she quickly became uncomfortable around him as he changed when he drank and he seemed "troubled", and a "prolific liar".

"Most nights he would drink [and] after a few drinks his whole mood would change," she said.

Women he met on Tinder would arrive at the house and the man would take them straight to his bedroom, she said.

He told the woman he owned a $900,000 BMW and a $1.3 million house in Sydney, and that his family were successful restaurateurs in Australia and were looking to buy an Auckland restaurant.

The stories didn't fit with the fact he rented a $170 room that was so small it could only fit a bed and a small closet. He also quibbled over paying bond for the flat, accusing the other flatmates of ripping him off.

"It didn't take long to realise he was not who he said he was and that nothing he said was true," the woman said.

The three flatmates became so disconcerted by his behaviour that none of them wanted to be in the house alone with him.

One night one of their flatmates did find herself alone with him.

"I was on a lateshift and came home around 11pm. My flatmate messaged me when she heard me arrive home and asked me to come into her room. I went in and saw her and she had a knife in her bed. I asked what had happened. She told me that [the man] had been drinking and that she felt uncomfortable around him."

One evening when they thought the man wasn't home, the flatmates met in the living room to discuss how to get him to move out.

"We were talking about the situation and agreed that we were going to ask him to leave the next day. The thought was scary because we didn't want to confront him or for him to get angry."

But it turned out the man was home and in his room. He emerged with a bag slung over his shoulder and a sad look on his face and said his mum had just died and he had to urgently go to Sydney.

"The whole thing was awkward - we knew straight away he was full of shit but were happy at the thought he would be gone for a few days."

But the next day when the woman came home she could smell aftershave and knew he had been there.

All his possessions were gone and the flatmates quickly had the locks changed.

However, the man then started messaging one of the flatmates telling her he was going to ruin all of their lives.

The woman had left New Zealand to live in the UK by the time Grace Millane went missing in December 2018, after going on a date with the man in central Auckland.

She remembers that the story of the search for Ms Millane was big news in the UK, as Ms Millane was from Essex in England.

"I was telling people it's such a safe country and that the whole thing was very out of the ordinary and weird."

Then a friend messaged her to say a man had been arrested and wasn't he her former flatmate?

"My stomach dropped, I felt sick for weeks after. It's an odd thing to say but when I heard [the man] had been arrested it all kind of made sense to me.

"Initially I was thinking, what sort of person could do such a thing? But then when I found out it was him, I thought, oh right - he's the sort of person that could do that."

She said she felt sick every time she read about the case and she thought of Ms Millane's family often.

"I think if it was not Grace it would have eventually been someone else that would have crossed paths with [the man]".

The woman said she felt relieved after hearing the man had been found guilty.

"I was hopeful the jury would see the kind of person he was and they have."