Freed journalist Peter Greste has told how he struggled to leave behind two colleagues in an Egyptian prison.

For more than a year, the three jailed Al-Jazeera journalists did their best to prepare for the unsettling possibility that one of them would be released, while the others were forced to stay.

But when that day actually came, Mr Greste struggled to leave behind the men who had become his brothers.

"See you when I see you," he told his colleagues, Mohamed Fahmy and Baher Mohammed, just before he left the prison on Sunday after 400 days behind bars in a case widely condemned as a sham by human rights activists.

Today, Mr Greste returned home to Australia, relieved and jubilant in his freedom, but still grappling with the reality that Mr Fahmy, an Egyptian-Canadian, and Egyptian Mr Mohammed remained trapped in their cells.

"You can imagine after 400 days in prison with these guys, we're very close and it was very difficult to leave them behind," the 49-year-old told reporters in the Queensland state capital of Brisbane, flanked by his family.

"But I'm grateful to be out. I trust that they will follow in due course ... It's going to take some further efforts, but we'll see them out. And when we do, I'm going to party with them very, very hard indeed."

The three journalists were arrested in 2013 over their coverage of the violent crackdown on Islamist protests following the military overthrow of President Mohammed Morsi.

Egyptian authorities accused them of providing a platform for Mr Morsi's Muslim Brotherhood, now declared a terrorist organisation, though officials never provided concrete evidence.

Canada said this week that Mr Fahmy's release was imminent but gave no timeframe.

The three were stunned by the judge's decision to convict them, Mr Greste said.

But as they waited out their sentences, they focused on staying physically and mentally healthy by working out regularly and supporting each other through the darker days. They were not abused, and were treated with respect, he said.

Mr Greste also began pursuing a master's degree in international relations while in jail, working with materials posted to him by an Australian university. At no point did he believe he would have to serve his full seven-year sentence.

"Then as now we were confident of our position, of our innocence," he said. "And we were confident that the process, if it was followed through to its logical conclusion, could only see us free."

Mr Greste often meditated, letting his mind drift to happier days spent at the beach with his family.

When he and his brother Mike arrived in the Mediterranean island nation of Cyprus, where they spent two days recuperating before returning to Australia, he could not wait to feel the sand between his toes.

Now safely back in Australia, Mr Greste said his priority is ensuring his colleagues' release.

He added: "I don't want to give this up - my job up. I'm a correspondent, it's what I do.

"How I do it, whether I actually do go ahead with it, I don't know. That's the way I feel right now."

His mother Lois - who, along with her husband Juris and their sons have spent a year tirelessly fighting for Mr Greste's release - said she has always believed her children should follow their passions.

"At the same time," she said, pausing to laugh, "he's got to know that we are not going to go through this again!"

Meanwhile, the families of Mr Fahmy and Mr Mohammed remained hopeful their loved ones would also be home soon.

Relatives of Mr Fahmy said the authorities had demanded he give up his Egyptian citizenship as a condition for his release.

President Abdel-Fattah el-Sissi issued a decree last November granting him the power to deport foreign defendants convicted or accused of crimes.

But Mr Mohammed, 31, who received the longest sentence in the case - 10 years - has no second citizenship and his family worries that his fate as an Egyptian is less clear.

Married and a father of three, he lives in Cairo. He covered the 2011 Libyan uprising before joining Al-Jazeera as a producer, and his father was at one point the manager of the Muslim Brotherhood's television channel, named January 25, which was launched after Egypt's 2011 uprising.

Lawyer Mohammed Abdelaziz, director of the Cairo-based al-Haqanya legal centre, said Mr Mohammed's case is still pending in Egyptian courts.

"His situation is different because he only has Egyptian citizenship," he said. "He is now awaiting proceedings with a different court, and his freedom depends on that case being finished."