The room had been deadlocked from the inside.
But Chief Coroner Deborah Marshall, in her findings released publicly today, determined Ellwood died around February 28, 2018.
In a separate coroner's findings, Hamilton's death was established as a suicide.
Police first labelled the deaths "unexplained" but later clarified that the case was not being treated as a homicide.
The pair, police told reporters, were known to each other and detectives were not looking for anyone else over their deaths before handing the case to the Coroner's Office.
Police also confirmed to the Coroner that Hamilton was a convicted rapist, who was jailed in 2007 for five years after he strangled a woman until she lost consciousness before the attack.
Further details of Coroner Marshall's full report remain suppressed.
Who was Tania Ellwood?
Ellwood's father Bruce told the Coroner his daughter was a "lovely kid" who sometimes pushed the boundaries.
She had suffered from nightmares after nearly drowning during childhood, he said.
The Coroner's report remarked she had "excelled" at poetry and art.
"Most of her poetry was about death and the afterlife."
During her working life, Ellwood played a small part in Shortland Street and worked as a personal shopper.
"For a short time, she trained as a flight attendant in the United Arab Emirates but returned to New Zealand and stayed with her parents for about five years until she was 37 years old."
At the time of her death, she was a sickness beneficiary who had been living in Sandringham with her partner Ira Heyder.
Her disappearance
Ellwood withdrew $440 from a Newmarket bank and went to a hair salon on February 28, something she was known to do every Wednesday.
Her hairdresser, Claudia, spotted her at a nearby cafe drinking some wine before their appointment.
According to the Coroner's report, Claudia believed her long-term client was intoxicated and speaking loudly when she saw her at the salon about 10am.
Ellwood told her hairdresser she intended on meeting up with an "ex" later that morning.
Claudia knew who she was talking about "Roman" who had also previously visited the salon.
Ellwood had sometimes called him "Romey", a man that was her "true love".
When she left she handed over a $20 tip - something she had never done before.
Ellwood then went to go play on the pokie machines at a Mercury Lane bar, where she met Hamilton with a still unknown second man.
The pair, however, began to argue before Ellwood left to have a smoke.
She bumped into her friend Veronica on Karangahape Rd and told her she was waiting for a "guy", the coroner's report reads.
The pair had not seen each other in about two years and the meeting was soon cut short.
"Here he comes, you should go, I don't want you to meet him," Ellwood said, according to Veronica, who looked back and saw a man smiling as he approached Ellwood.
CCTV footage also showed Ellwood and Hamilton again meet on Karangahape Rd at about 2.30pm.
They then began to head towards Dryden Lodge.
"There is nothing in their demeanour to suggest coercion of either party," the Coroner said.
A grisly discovery of two bodies
Blowflies began to gather in the window of a room darkened by closed curtains at the lodge on March 2.
The caretaker noticed and also saw there was no light on in the room - he couldn't hear voices or music.
He knocked on the door of room number 25 the next day but there was no response.
A tenant from the adjacent room also began to complain about a smell emanating from the room.
On March 5, the caretaker tried to open the door with a key but found it had been locked from the inside.
He went around to the window and pushed aside the curtain.
There he saw Hamilton standing naked in the room, mumbling and holding a white sheet.
The caretaker left but would return the next day with the Dyrden Lodge's owner.
They found two bodies in the room and called the police.
Evidence considered by Coroner Marshall showed Ellwood had died before Hamilton.
"There are several possible causes of death but given the post mortem results, any suggestions of a cause of death would be speculative."
WHERE TO GET HELP:
If you are worried about your or someone else's mental health, the best place to get help is your GP or local mental health provider. However, if you or someone else is in danger or endangering others, call 111.
If you need to talk to someone, the following free helplines operate 24/7:
DEPRESSION HELPLINE: 0800 111 757
LIFELINE: 0800 543 354
NEED TO TALK? Call or text 1737
SAMARITANS: 0800 726 666
YOUTHLINE: 0800 376 633 or text 234
There are lots of places to get support.
For others, visit: https://www.mentalhealth.org.nz/get-help/in-crisis/helplines/
