A convicted child sex offender has confirmed that he attended the search site for missing four-year-old boy Gus Lamont shortly after the boy disappeared, angering locals. 

Daily Mail can reveal that Trevor Roberts - an 88-year-old mechanic who admits to having 'skeletons' in his closet - gained access to the remote property at Oak Park Station where the search was being conducted. 

Roberts, a mechanic who lives in a shed just off the town of Yunta's main street, said that he delivered food to SES workers who were looking for Gus, after a request by the local pub in the days after the boy mysteriously vanished last year.

Locals expressed outrage that Roberts had made the deliveries, given the circumstances, and alleged that he 'gained access to the family property unchecked and unnoticed by police'. 

Gus was last seen playing on a dirt mound at the family property in the remote mid-north of South Australia at about 5pm on September 27 last year. 

Despite the state conducting the largest missing persons search in its history on the vast property owned by Gus's two grandparents, no trace of the child has yet been found.

And this week, just over seven months since her son mysteriously vanished, Gus's mother was spotted publicly for the first time, on a suburban Adelaide street with her youngest child.

On the same day, Gus's grandparent Josie Murray - a transgender woman - was due in court on a firearms charge, Jessica Murray was seen out and about with Gus's younger brother Ronnie, aged about 20 months old. Ms Murray politely declined to comment. 

South Australia Police declined to comment specifically on Roberts' presence at the Murrays' property during the search for Gus, but the child sex offender himself confirmed it to the Mail.

Meanwhile, angry residents in Yunta, and on properties along the road to the Gus's family's 60,000-hectare station in the northern Flinders Ranges, are still demanding answers.

Roberts' visit: What locals, police and the man himself say  

Roberts' visit followed Gus's disappearance on a Saturday evening, which prompted community and family members to join in the initial ten-day search with SES workers, police, Australian Defence Force members, Aboriginal trackers and trailbike teams.

Days into the operation to find Gus, the only pub in the town, the Yunta Hotel, some 40km north of Oak Park, prepared meals for up to 75 SES volunteers who were on site.

Despite having a tiny population of about 60, Yunta is the last major stop for road trains on the Barrier Highway to Broken Hill, NSW, and its pub and roadhouses do a roaring trade selling meals to truckies stopping for fuel.

The Yunta Hotel asked Roberts to use his vehicle to deliver the food to the SES on the Oak Park property. 

Shayne Clark, the publican, confirmed Roberts drove the food supplies over to the SES 'with a staff member', as no one with a driver's licence was working that day. 

'He didn't go on the property - he went to a checkpoint where they handed over the meals,' he claimed.

Mr Clark said he was interviewed by the Yunta police officer the following day and he claimed the fact that Roberts was a convicted paedophile was 'really irrelevant'.

'The only thing that matters is Gus.'

One neighbour who knew about Roberts' criminal past told the Daily Mail that as soon as she had heard Gus was missing, she feared that Roberts may have been responsible.

'Then we heard he had spent the night Gus vanished in hospital, but police told us later they had cleared him of any involvement in a possible abduction.' It is not suggested otherwise.

Roberts confirmed to the Mail that he had delivered the food to searchers at Oak Park Station.

Asked about whether he was a convicted child sex offender, Roberts said, 'yes, but that was a long time ago. 

'A lot of people hate your guts if you do something and then you find out they all have skeletons in their closet.' 

Roberts said he had never been to Oak Park Station before the food delivery, and did not know Gus, saying 'no (I never met the little boy). Poor little bugger.' 

He added: 'That place has got mine shafts everywhere.'

Roberts said he had met the little boy's father, Josh, years ago. It's not suggested Josh Lamont had knowledge of Roberts' past. 

'He came to me in the workshop at the (Yunta) Race Club and wanted me to fix his motorbike,' Roberts said.

The Mail asked South Australian Police if they knew that a convicted sex offender was involved in the search for Gus, whether it was true Roberts accessed Oak Park Station ‘unchecked and unnoticed by police', and what was  Roberts' history of child sex offending.

The Mail also asked police to confirm if they had cleared Roberts of any involvement in Gus's disappearance. 

South Australia Police did not respond specifically to the questions about Roberts' actions during the search operation, nor his criminal history, saying that there was 'no update on the Gus Lamont investigation' .

But in a statement, they added: 'All individuals on the ANCOR database who lived within a significant radius of Oak Park Station were interviewed by ... detectives. All have been eliminated from the investigation.'

ANCOR is the Australian National Child Offender Register. Roberts - who was in hospital after suffering complications following an angiogram - said that he hoped to return home to Yunta soon. 

Gus's grandmother Josie Murray, 75, is facing a criminal charge unrelated to her grandson's disappearance that arose from one of the police searches for evidence at Oak Park Station. 

Police charged her with possessing an illegal firearm sound moderator, or silencer - a charge which carries a maximum penalty of up to a $75,000 fine or 15 years imprisonment - after inspecting licensed weapons Ms Murray owns. 

Police laid the charge two months ago after Task Force Horizon, the case investigative unit, allegedly found the device upon returning to Oak Park Station to search for further evidence about Gus's disappearance. 

Ms Murray was listed at Peterborough Magistrates Court, 90km southwest of Yunta, on Wednesday morning, but her appearance is now set down for next month in an Adelaide court.

SA Police have confirmed they have 'all but ruled out' the possibility that Gus simply wandered off. 

In February, South Australian Police Commissioner Grant Stevens claimed two members of Gus's family had been 'not co-operating' with authorities investigating the disappearance, but underlined the fact that this was not the boy's parents, Jessica and Josh.

Josie Murray and Gus's grandmother Shannon Murray released a statement through lawyers saying they were 'absolutely devastated' by this assertion. 

'We are absolutely devastated by the media release of SAPOL Major Crime. The family has co-operated fully with the investigation and want nothing more than to find Gus and reunite him with his mum and dad,' the statement read.

SA Police officials have said they could still conduct another sweep of the property in the future to try and find clues about Gus's disappearance.