Missing man Matt Levenson was a "bit of a princess" and became unhappy when he didn't get his own way, his former boyfriend has told an inquest.
And that's why the 20-year-old disappeared - possibly to Thailand - after a drug-fuelled night out, Michael Atkins responded when asked why the young man would leave unexpectedly.
This was the much-awaited evidence of Mr Atkins, who in October 2009 was acquitted of Mr Leveson's murder.
He entered the witness box on Monday at a continuing NSW coronial inquest into the September, 2007 disappearance.
He spent the day being grilled after losing a legal challenge against being called to give evidence and may be cross-examined by Matthew's father, Mark, on Tuesday.
During his evidence on Monday, the inquest finally heard Mr Atkins' version of events.
Under questioning from counsel assisting Lester Fernandez, Mr Atkins - then 44 - said the pair left ARQ sometime between 2am and 3am on September 23, 2007, because Matt had taken too many drugs.
"He was pulling faces and scrunching (his) face," Mr Atkins said.
The men had taken the drug known as GBH and ecstasy and were partying hard but Mr Atkins said he decided to exit when he saw his boyfriend had developed "manky face" - which he said happens to those who consume too many drugs.
The men then drove home and went inside their Cronulla unit.
"We just did the normal things we did when we came home," he told the inquest, adding that his memories of that morning were a bit of a blur.
Questions then turned to what Mr Atkins thought may have happened to Mr Leveson, whom he has described as his greatest love.
"I'm not sure, really," he said repeatedly.
"I always thought that he went to Thailand. He just liked to travel."
Why Thailand, he was asked by Mr Fernandez.
"To start a new life ... like starting afresh," Mr Atkins said.
Again Mr Fernandez asked, why would he leave?
"He was bit of a princess and got the shits when he didn't get his own way," Mr Atkins said.
Several Leveson supporters, who had packed out Glebe Coroner's Court, scoffed as Mr Atkins gave evidence.
On September 25, Mr Atkins and Mr Leveson's parents, Mark and Faye, reported him missing after he failed to turn up for work.
"I thought he would be back the next week," Mr Atkins said.
"Always thought he would come back."
During earlier hearings, CCTV footage showed Mr Atkins buying a mattock and gaffer tape later on the last day on which Mr Leveson was seen alive.
Mr Fernandez told the inquest a hardware shop receipt for the purchase carried Mr Atkins' DNA and was found inside Mr Leveson's car, which was later discovered abandoned in the Sutherland area.
When asked if Mr Leveson was alive, Mr Atkins said he holds a "tiny hope" Mr Leveson will come back.
The inquest is continuing.
