Michael Atkins – the last known person to see Mr Leveson alive nearly a decade ago – was handed a mattock and asked to demonstrate how he would use it during a dramatic inquest hearing on Wednesday.

Mr Atkins, 53, claims he bought a mattock and tape from Bunnings in the Sutherland Shire on the same day that Mr Leveson vanished because he had "always been a keen gardener" and "always wanted to start a garden".

He was found not guilty of murder and manslaughter by a jury in 2009 after a trial where it was alleged he had bought the equipment to help him dispose of Mr Leveson's body.

During his third day of evidence, Mr Atkins was handed the type of mattock he purchased and then stood up and demonstrated digging with it, prompting friends of Mr Leveson's to leave the court in distress.

Mr Atkins was also handed tape and tomato plants and was asked to demonstrate how he planned to connect his own seedlings to stakes, as he claimed was his intention for the tape.

" What else are mattocks used for?" counsel assisting, Lester Fernandez, asked.

"That's all I thought ... digging up gardens," Mr Atkins responded.

"Digging a grave would you agree?" Mr Fernandez continued.

"Could be."

"Somewhere like the national park down south where you live, agreed?" Mr Fernandez said.

"Could be anywhere."

Mr Atkins has been compelled to enter the witness box for the first time but has immunity from prosecution for any admissions he might make.

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, and his parents hope the inquest will reveal where his buried.

Addressing the question of why he bought the tape and mattock for the first time, Mr Atkins said he was growing zucchini, tomato and beans on his balcony and planned to dig up a garden plot at the base of his Cronulla unit.

He was repeatedly questioned about his botanical knowledge. Asked what could threaten his planned vegetable garden, Mr Atkins said dogs, cats and possums.

"What about snails?" Mr Fernandez asked.

"I didn't think about snails," Mr Atkins responded.

"Keen gardener unaware of snails?"

"Not unaware, just didn't think about it at this point."

Mr Fernandez presented Mr Atkins with eight different plant ties that could be purchased at Bunnings, and questioned why Mr Atkins had opted for a general purpose tape used for " repairing, binding, insulating, reinforcing".

Mr Atkins was also asked why he had opted for a mattock, usually used to dig trenches and for cutting roots, when there were hoes, trowels and shovels in the gardening section at Bunnings.

"I wonder if I could ask you to stand up please ... hold that mattock in your hand and lift it up ... That's a fairly heavy item isn't it?" Mr Fernandez said.

The inquest heard that Mr Atkins did not have any other tools to help him create his garden.

"And on that Sunday you decided to buy a mattock and cloth tape, correct?" Mr Fernandez said.

"Yes."

"That's how you were going to do your gardening was it?"

"Yes."

The inquest also heard that a friend of Mr Atkins had given evidence that he had never shown "any interest whatsoever" in her own lush garden and that the pot plants he kept "looked neglected".

Mr Atkins has previously told the inquest that he and Mr Leveson left ARQ nightclub together, went home, and went to bed.

He claims the last time he saw his boyfriend was later that day after, after he returned from Bunnings, and he thought Mr Leveson was preparing to go out.

The day after Mr Leveson went missing, Mr Atkins was captured on security footage buying new shoes.

Asked why he needed to buy new shoes on that day, Mr Atkins said he was not sure and could not remember going there.

"I was just being an eternal optimist I think," he said.

"I tend to be like that, I was just thinking he was going to come back."

The inquest has also heard that Mr Atkins had sex with two men in the following days, despite sending multiple messages to Mr Leveson's mobile phone expressing his concern for his whereabouts.

The inquest will continue on Thursday.