He asked the girl which school she attended. Police replied “parra high”, and Wanstall said, “Nice”.

Wanstall exchanged mobile numbers with the purported teenager and stated, “Im so sacred [sic] you’re the police lol” and that he would “be in jail”.

He inquired about her favourite movie, asking “Disney Princess?” Wanstall also messaged, “Wish I could see you in uniform” and “think you should be in dress not uniform ... so it looks less suss”.

The court heard Wanstall told a forensic psychiatrist that he had tried to make his former partner jealous and had hoped posting the advertisement would attract her attention.

Judge Andrew Colefax said it was a “preposterous explanation”, noting Wanstall was a “highly intelligent man” and the post was anonymously placed.

“There’s no rational reason that a reader would attribute that advertisement to your client,” the judge said. “I just cannot accept it.”

He said Wanstall had done more than place an advertisement, he had “engaged in highly sexualised communications over a period of time with someone he thought was 14”, arranged to meet the child and had gone to a location with money in his pocket to pay for services.

Colefax said a recurring theme with offenders like Wanstall seemed to be “that these men are unable to face the truth”.

“They often come up with bizarre explanations to themselves as to why they’ve done what they’ve done,” he said.

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In response, defence barrister Nicholas Baltinos said some “pillars of society do ridiculous things”.

He said Wanstall had a lack of success with relationships and was “not adept” at handling their breakdown, and had discovered his former partner was also online “with dating sites and the like”.

“It may not be as implausible as we might imagine,” Baltinos said.

Arguing a case of exceptional circumstances to avoid full-time imprisonment, Baltinos said Wanstall had an impressive and stable career, that his elderly mother would suffer hardship, and further asked the judge to accept Wanstall had been drinking.

Baltinos submitted that it was not a “normal” case of its kind, and that there was no evidence Wanstall had stored or viewed child abuse material or belonged to a criminal ring of such kind.

Crown prosecutor Alex Brown said there was an inconsistency between Wanstall’s account that he had been intoxicated and some messages being sent on weekdays during school hours, presumably while he was fulfilling his duties as deputy principal.

Brown suggested the judge would not find intoxication as an explanation, rather that the dominant factor driving Wanstall’s behaviour was a “sexual interest in teenagers”, including as young as 14. The prosecutor said it was not impulsive or spontaneous behaviour and had lasted a number of days, giving Wanstall “ample time to reflect on his conduct”.

Wanstall will be sentenced at a later date.

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