He consistently claimed he didn't know what happened to his boyfriend Matthew Leveson, who vanished after leaving a Sydney nightclub 10 years ago.

In truth, Mr Atkins, concerned about his reputation, dumped his younger partner's body in a shallow grave and kept quiet about it for years.

Now the "selfish" reasons for Mr Atkins doing so have finally been laid bare.

The inquest into Mr Leveson's disappearance resumed on Wednesday, three months after police uncovered his skeleton in the Royal National Park.

The case leapt forward last November after Mr Atkins agreed to tell police what he had done after complex immunity deals protecting him from prosecution were sewn up.

The NSW Coroner's Court heard on Wednesday how Mr Atkins attributed his former partner's death to a drug overdose that could damage his reputation.

The electrician told police in a late night interview on November 10 that, in 2007, he was an older partner with a younger boyfriend and he had only recently come out as homosexual.

His mother, who brought him up in a devoutly Catholic home, also didn't know he was gay, Mr Atkins told police.

In summarising Mr Atkins's 21-page statement, Detective Chief Inspector Gary Jubelin said the 44-year-old claimed he woke up on the morning of September 23, 2007, and found Mr Leveson dead in bed.

The pair had had a "falling out" at ARQ Nightclub in Darlinghurst the night before and had slept in separate rooms.

Mr Atkins told police he saw a bottle of the drug GHB in the kitchen and assumed Mr Leveson had had a drug overdose.

He stayed with his body for a few hours before going to Bunnings Warehouse and buying a mattock and duct tape.

"He waited until it got dark, around midnight, he wrapped Matt's body in a blanket or sheet and carried it down to the car port," Inspector Jubelin explained.

Mr Atkins told detectives he pulled the boom box out of Mr Leveson's car boot and put his body in there.

From his Cronulla unit, he drove south until he pulled off McKell Road, near a hairpin bend, in the Royal National Park.

"He went into the bush and determined that was a suitable place to bury Matt's body," Inspector Jubelin said.

For the next 30 minutes, Mr Atkins worked on digging a hole about two metres long by one metre wide.

He then rolled his boyfriend's body into the grave and filled it in with dirt before dumping Mr Leveson's car at a gay beat nearby.

A few days after that, Mr Atkins travelled to Newcastle and had sex with another man, a move Detective Jubelin labelled "morally bankrupt".

When Mr Atkins was asked about the impact Mr Leveson's death had on his life, he told police: "I don't think I could love anyone like I loved him ... it weighs on me everyday."

Mr Leveson's parents, Mark and Faye, listened intently as the chilling claims were recounted.

Mrs Leveson wiped away tears as she emerged from court and raised questions about Mr Atkins's honesty.

"He had him (Mr Leveson) in the unit with him for hours and didn't even call triple 0," she said. "That's if you can believe what he said and I don't..."

Counsel assisting the coroner Tim Game, SC, raised concerns about the credibility of Mr Atkins's assertions and said it wasn't being "relied upon for hearsay purpose".

The court heard there was no forensic examination that could prove Mr Leveson died of a drug overdose.

After he provided his statement to police last year, Mr Atkins drew a diagram of the approximate whereabouts of the grave site.

He also underwent hypnosis in a bid to remember the exact location of the grave after initial searches were fruitless.

He also travelled with homicide detectives to the national park where he walked through the bush drawing on memories from nine years before.

At one point, a 70 kilogram mannequin was brought to the search site. Mr Atkins was then asked to demonstrate how he carried Mr Leveson's body from the car to where he buried him.

It wasn't until the third search on May 31 that a backhoe uncovered Mr Leveson's skeleton.

Mr Atkins's immunity deal hinged on him making sure police found Mr Leveson's body.

He was compelled to give evidence at the inquest after he was issued a section 61 certificate under the NSW Coroner's Act last year.

That meant his evidence could not be used against him in future proceedings. It didn't protect him from perjury or contempt of court charges.

Inspector Jubelin said police believed Mr Atkins then lied during his evidence at the inquest and police used that as a negotiating tool.

The NSW Attorney General agreed to grant Mr Atkins immunity from perjury charges if he told police where the body was.

Mr Atkins made an induced statement, which gave him an extra layer of protection. Information in that statement couldn't be used against him.

It is unlikely Mr Atkins, who has stayed out of the public eye since Mr Leveson's body was found, will have to give evidence again.

Mr Atkins was acquitted in 2009 of Mr Leveson's murder and manslaughter.

The inquest resumes on Friday.