A Canberra man who planned to sexually abuse children overseas when he was caught by an undercover cop, who posed as an English mother pimping out her three children online, told police he'd spoken of molesting them "purely as a fantasy".
Federal police arrested Nathan Sertori, 36, at Sydney Airport and stopped him boarding an international flight after a tip-off from INTERPOL sparked an investigation from Australian child protection officers in June 2016.
Sertori had planned to fight the charges but later pleaded guilty in the ACT Supreme Court to planning to have sex with a child outside Australia and transmitting child pornography. He faced court for a sentence hearing on Thursday.
The case is believed to be the first time the Commonwealth offence of planning to abuse a child overseas has been prosecuted in the ACT.
Court documents said Sertori had online conversations, which began on an incest website, with an undercover British police officer posing as "Sadie" about plans to meet in London and sexually abuse the woman's three children in late July.
In a series of explicit exchanges, he spoke of plans to have sex with the woman and abuse her two daughters, aged 12 and 14, and her son, aged 10.
"The accused had a particular interest in Sadie's daughters," the documents said.
Police who investigated the man's online profile, under the username of "Dtyungman", discovered he also belonged to teen sex and child rape online discussion boards.
An IP address was used to track the online profile to Sertori's family home in Holt. Police matched his online profile description with images on social media and his passport photograph.
He was arrested after Australian Border Force officials alerted police Sertori had flown out of Canberra and was booked on a flight with his mother from Sydney to Dubai on July 12.
In a police interview, Sertori admitted he'd contacted a woman online about engaging in sexual activities with her two daughters and said she'd offered her son for him to rape.
He said he knew the children were all younger than 18.
But he told police he asked the woman about having sex with her children "purely as a fantasy" and had no intention of meeting up with them in London. He said he also planned to travel to Paris and Copenhagen with his mother.
He'd asked for photos but planned to send them to police, court documents said. He was charged when the interview finished.
During a search of his home the next day, police seized his computer and electronic devices, child exploitation material from online chats, and a travel itinerary.
The court on Thursday heard the last online conversation of a sexual nature had been on June 24, nearly three weeks before Sertori's arrest.
Defence barrister Alyn Doig argued Sertori didn't necessarily intend to carry out his fantasy at the time he boarded the plane and "may well have come to his senses" by that time.
But federal prosectors, who called for an immediate term of imprisonment, said Sertori had given the undercover police officer a date and shared where he would be staying in London.
Mr Doig noted the child exploitation material had been written comments and didn't include images. He said the offender's trip with his mother had not been planned for the purpose of child sex abuse.
He said Sertori, who had been assessed as a low risk of general reoffending, had shown insight into his crimes and sought psychological help.
"He's well on his way to being as rehabilitated as he can be, given the circumstances."
Mr Doig urged the court to consider an intensive corrections order, which would allow Sertori to serve his sentence in the community.
Justice John Burns will hand down his sentence next Thursday.