While the 54-year-old’s charges remain sealed, his arrest on October 21 in Orange came at the same time as reports emerged that ex-British and Australian pilots were instructing their Chinese counterparts. He formerly operated Top Gun Australia, an adventure flight business.

His defence lawyer, Dennis Miralis, said in November, “In 22 years of practising criminal law with a specialisation in extradition, I have yet to see something as remarkable as this.

“We’ve been told the Australian Federal Police do not regard him as a risk. We’ve been told the Attorney-General’s department do not regard him as a risk.

“We are concerned that there may have been some foreign interference encouraging the corrective services minister to take this dramatic course of action.”

He added his client was a “proud Australian” who no longer holds US citizenship, adding that Duggan had been denied medical treatment.

Barrister Trent Glover, representing the US, said in response this was the “ordinary, usual extradition process”.

The matter will now be dealt with by a magistrate in January, with the US alleging Duggan breached money laundering and arms export control laws.

His case followed reports in The Times and The Australian newspapers that China had been reaching out to former UK and Australian pilots.

Defence Minister Richard Marles pledged an investigation into the alleged practise, and shortly afterwards told journalists that “enough evidence” had emerged to warrant a review of current laws.

However, Marles crucially refused to say whether the involvement of any Australians had been confirmed.

“The information provided to me so far presents enough evidence to warrant the need for a detailed examination into the adequacy of current Defence policies and procedures addressing this matter,” Minister Marles said in a statement.

He added former personnel had an “enduring obligation” to protect national secrets, and changes to the law would be made if “weaknesses” were found.

“I want to make this point. For those who do come into possession of our nation’s secrets, either through service in the Australian Defence Force or, indeed, service in any other part of the Commonwealth, there is an enduring obligation to maintain those secrets for as long as they are secrets, which persists well after their engagement with the Commonwealth, and to breach that obligation is a very serious crime.

“And that is clear and unambiguous.”

Currently, ex-service personnel can only work with overseas militaries with permission from Australia.