Ricketson landed safely, aboard a Thai Airways flight, in Sydney just before 8pm, physically and emotionally exhausted, after spending the previous day in immigration detention.

As Ricketson, 69, emerged to face the waiting media, he wore a big smile. “My 15 minutes of fame!” he exclaimed as he pushed his baggage trolley in front.

“It’s fantastic to be back in Australia. 48 hours ago I was in a maximum security cell, so this is all a bit of a culture shock," he said.

Mr Ricketson thanked his family for their support over the past 15 months of his ordeal.

"They’ve supported me enormously the last 15 months. Without their help I don’t think I’d be here."

The documentary filmmaker, found guilty of espionage last month in a court case widely criticised as a sham, has had a dramatic reversal of fortunes in the 48 hours since receiving a royal pardon.

Ricketson reserved a special thanks for his son Jesse and partner Alex for moving to Cambodia to help secure his release.

"I appreciate that enormously because that’s a huge sacrifice and an indication in action of the love that they have for me."

The ordeal began in June 2017, when Ricketson was arrested for flying a drone over an opposition rally, taking photographs of the heavy security presence. Having lived and worked in Cambodia for 22 years, Ricketson's work largely focused on the underprivileged, including documenting the lives of children who scavenged on a large rubbish dump on the outskirts of Phnom Penh.

He was an outspoken critic of the so-called Cambodia solution, a controversial scheme under which Australia resettled four refugees.

Ricketson spent a year in pre-trial detention, and his trial in August was widely criticised by observers and human rights advocates as unjust.

Ricketson said his love for Cambodia was undiminished, pledging to return as soon as his health allowed.

"My relationship with Cambodia has been a 20-year love affair and the last 15, almost 16 months has been like a lovers' quarrel," he said.

"I'll be going back as soon as I can but I'll need to recover, obviously. I need to spend some time with myself and some time with my family."

"I don’t love Cambodia any less now as a result of what has happened. In fact if anything I love it more."

Asked what he was most looking forward to doing, he was unequivocal: “A swim in the ocean!”

Daughter Roxanne Holmes said it was “wonderful” to have her father home.

"We’re all really elated, excited," she said.

She told Fairfax Media immediately after the pardon was announced that it came "out of the blue" but the family was incredibly grateful for the support they had received, including more than 107,000 people who signed the Change.org petition.

"But the first thing he will want to do is to have some space, get some medical treatment," she had said.

Ricketson confessed to being “exhausted”.

"I don’t want to wind up saying the wrong things in a state of being in tiredness and shock."

Asked whether he was frustrated by the Australian government's handling of his case, Mr Ricketson was cagey.

“Let me just say there is room for improvement, but I’ll leave it at that. I really need to go home and go to bed.

"I do have a good story to tell, but now at the airport is definitely not the right time to tell it.”

Phil Robertson, deputy Asia director of Human Rights Watch, said "the 14 months of hell" Ricketson endured should not be forgotten in light of the pardon.

“No one should overlook the bogus criminal charge of ‘espionage’ and how the Cambodian government cruelly used him as a pawn to give substance to their fantasy political conspiracy of a so-called ‘colour revolution’," Mr Robertson said in a statement.

"Apparently now that Prime Minister Hun Sen has destroyed the political opposition and garnered all the seats in Parliament, he gave the green light to let Ricketson go. This very welcome release does not erase the shameful procession of farcical questions and ‘evidence’ that a Cambodian kangaroo court used to convict Ricketson nor the reputational damage this case has brought to the Cambodian judiciary.

"I hope that after he is reunited with his family, he will give a full reporting about all that has happened to him, and the injustices he suffered at the hands of the Cambodian government and judiciary. Obviously, we wish him all the best and hope he makes a full recovery from this long and unjust ordeal."

Australian journalist Alan Parkhouse first encountered Ricketson seven years ago when he was the editor-in-chief of the Phnom Penh Post, and has covered the court case extensively.

"I'm very pleased James has been released," Parkhouse said. "But it's wrong that he was even arrested in the first place. And it's a travesty he had to spend so long in such difficult conditions as Prey Sar prison. Many people in Cambodia wonder if there was an ulterior motive for his arrest. He was never a spy and liking or even supporting the former opposition party is not a crime."