Michael Atkins, 53, who has been acquitted by a jury of the murder and manslaughter of Mr Leveson, told a coronial inquest he had "always been a keen gardener" and "always wanted to start a garden".

There was audible laughter in the court room as Mr Atkins, who is the last known person to have seen Mr Leveson alive, said he needed the equipment because he was growing zucchini, tomato and beans on his balcony.

Mr Atkins has never given formal evidence, either in court or to police, about the purchases from Bunnings in Taren Point, although they formed a key piece of evidence against him in his murder trial in 2009.

Mr Leveson, 20, was last seen leaving the popular ARQ nightclub in Sydney's Taylor Square with Mr Atkins, then 44, in the early hours of September 23, 2007. His body has never been found.

Mr Atkins was compelled to enter the witness box for the first time, with immunity from prosecution, after a ground-breaking ruling by Deputy State Coroner Elaine Truscott who found that he would "likely be able to give important evidence about the manner and cause of Matthew's death".

He told the inquest that he and Mr Leveson had returned from the nightclub together and later that day he went to Bunnings because he had seedlings germinating on his balcony and had always wanted to start a garden at the base of his unit block. He was in the store for about 30 minutes, made two purchases and paid with cash.

"What would you use a mattock for?" counsel assisting, Lester Fernandez, asked Mr Atkins.

"To dig up the garden," Mr Atkins responded.

"What did you need duct tape for?" Mr Fernandez asked.

"I was going to … I [had] seen it on a TV program where they tie it around plants as they are growing," Mr Atkins said.

Mr Atkins denied he paid for the duct tape and mattock in cash rather than on a credit card because he was trying to avoid creating an electronic record of his purchase.

He claims the last time he saw his boyfriend alive was after he returned from his Bunnings trip, and that he thought Mr Leveson had been preparing to go out again.

Earlier in the inquest hearing on Tuesday, Mr Atkins said he wanted to leave ARQ because he was worried about how many drugs Mr Leveson had taken and they had driven back to their Cronulla unit together.

But the inquest heard that security footage captured Mr Atkins and Mr Leveson leaving ARQ together before Mr Atkins returned to the nightclub without him 55 minutes later.

Mr Atkins said he had "no memory" and could not say where he and Mr Leveson were during the period.

He also said he did not know why, shortly before leaving the club, he had sent Mr Leveson a text message saying "I already apologised three times" and that he needed to get more drugs for a friend.

The inquest heard the last text messages Mr Leveson sent were about Mr Atkins.

"Mike's having a f---ing cry, he is taking me home and won't let me stay! F---ing c--t!" a text message at 3.20am said.

"He needs to f---ing get over himself," another at 3.41am said.

Mr Atkins agreed that Mr Leveson was "shitty" but he denied they had a fight during the car trip home.

"I was trying to take Matt home for him to be safe," Mr Atkins said. "I was trying to just care for him but Matt wanted to go back."

"Did you do anything to Matt?" Mr Fernandez asked.

"No," he responded.

The inquest is due to continue on Wednesday.