Hand prints found near Glenbrook train station that an expert said were Indigenous and "culturally significant" have been exposed as fakes created by teenage brothers in the 1960s.
The rock art was discovered during work to remove a 20-tonne boulder which threatened the Blue Mountains railway line in late March. It extended the weeks of delays on the train line as buses replaced services.
An archaeologist, with a specialty in Indigenous heritage, said at the time that the multiple red hand prints were "culturally significant".
But in a letter obtained by the Gazette last week, a non- Indigenous man said he created the artwork 50 years ago. He and his brothers were paying homage to local Indigenous culture and he was now keen to "set the record straight".
The man, who lives in the Riverina region and has asked not to be identified, wrote the letter to Indigenous elders, including Gundungurra elder, Aunty Sharyn Halls, and it has been passed along to local historians and the Australian Museum.
In the letter he admits to creating the cave hand prints as a 13 or 14-year-old with his siblings in about 1969. He apologised for the "fuss".
"We loved Aboriginal culture and history and making the handprints was just another of our activities which imitated their culture," he writes.
"We ground some local red sandstone to make powder, mixed it with our saliva, rubbed it on our hands and simply stamped them onto the cave wall. I was amazed an expert did not realise they were not genuine as we did not stencil them, as Aboriginals would have, we just stamped them. We were not keen about putting the mix in our mouths, so we just rubbed it on our hands."
The man said they had had "no intention of offending anyone (and) no idea what fuss it would cause 50 years later".
"As kids we used to roam the bush enjoying its beauty and searching for signs of Aboriginal occupation. We made spears and even ground an axe head from stone".
Indigenous elder, Aunty Sharyn Halls, is the secretary of the Gundungurra Aboriginal Heritage Association which has an ILUA (Indigenous Land Use Agreement) over the site and said the experts had "made a terrible mistake and not consulted properly. They were so excited, they jumped the gun".
"The archaeologist [with Sydney Trains and the Office of Environment and Heritage] should have done her work properly," Aunty Sharyn said.
"People jumped the gun. I drove 500 kilometres to meet this guy recently to confirm the story. Make no mistake this guy is the person who did it when he was a kid with his brothers."
The artist said he spoke out as it was "important to maintain the integrity of registered sites and to have them verified by local Indigenous groups before being declared 'culturally significant'."
He also apologised "on behalf of myself and my brothers ... for any inconvenience suffered by local commuters and Sydney Trains staff" and hoped he had not offended any Indigenous people.
Sydney Trains has refused requests by the Gazette for an interview with Office of Environment and Heritage staff or the archaeologist.
Last month, when asked about the artwork's authenticity, a spokesman said they had commissioned a report into the finding at Glenbrook. He said it would have an "Aboriginal Cultural Heritage assessment".
The spokesman said the initial finding was "very much preliminary work. The last thing we wanted to do was blast away rock. We are going through the protocols ... working concurrently with the Office of Environment and Heritage".