As far as Tennis Australia could tell from the dodgy documents, Nguyen had only committed $811 worth of credit card fraud.

But TA discovered the ruse and reported their concerns to police in November 2023. Investigators charged Nguyen, again, with two counts of publishing false material.

Nguyen pleaded guilty to doctoring the documents this year and was ordered to face sentence in July.

He was not in Federer’s Dubai court this time, but rather Judge Michael Allen’s, in Sydney’s Downing Centre, as his lawyers handed up documents like psychological reports, an apology and a character reference on a Cecil Hills High School letterhead.

The documents were designed to lessen Nguyen’s looming punishment, but police prosecutor Matthew Aylward spotted striking similarities between two documents.

The signature on Nguyen’s apology looked suspiciously familiar to the signature of his colleague on a character reference letter. The grammar, too, was well below par for someone claiming to be a head teacher at Cecil Hills High.

“Mr Nguyen has expressed much remorse for his actions as he is very sorry for what has occurred and the affect [sic] his actions has caused harm to society,” the letter read.

“In my opinion, due to Mr Nguyen’s position being lost at Tennis Australia due to this offence, there will be very likelihood that Mr Nguyen will not be able to reoffend again.”

Aylward told the court he needed to contact the letter’s author, Nguyen’s colleague before the sentence could be handed down.

Nguyen began to message the other teacher desperately asking for “a favour” before Aylward could find his phone number.

“[It’s] a character reference of me that’s it. The letter is completed just say it has been signed by me and go from there,” Nguyen messaged his colleague.

“I want to help … can I at least see the character reference? What is this for?” the other teacher replied.

“Yes it’s regarding a police offence that I may have caused,” Nguyen said.

Nguyen bombarded the teacher, pressuring him to say he had written the letter in Aylward’s hand.

“Please just tell them you signed the letter and wrote it otherwise I’m farked man.

“This could be bad for me. Even like jail time not good.”

But the other teacher was firm, telling Nguyen “I can’t lie about this” and it was “better to be honest”.

The teacher told the prosecutor he did not write the letter and had only known of its existence for half an hour before he was contacted about it.

The case was delayed, detectives began a formal investigation and a week later charged Nguyen with perverting the course of justice.

Last week Nguyen was sentenced to nine months’ prison, but will not spend a day behind bars. Instead, he will serve an intensive corrections order until May 2025. He must do 100 hours of community service and seek mental health treatment.

TA said they provided additional information to the sport’s international regulator in January 2024 and severed all ties with Nguyen that same month.

A NSW Education spokeswoman said Nguyen was “no longer working for the department”.

“The department does not tolerate employees engaging in any form of criminal conduct,” the statement said.