Greste arrest a "nightmare": boss

The boss of detained Australian journalist Peter Greste has described the nightmare of having a reporter arrested and imprisoned overseas and praised the level of diplomatic support from Canberra.

Heather Allan, the head of news gathering for the Al-Jazeera English network, led an international press conference in London on Wednesday calling for the immediate release of Greste and his colleagues, detained in Cairo without charge.

"You are always worried about where your crews end up, either in jail, or kidnapped, or worse still, killed. It's always a foreign editors' worst nightmare," Allan said.

Greste, 48, and colleagues Mohamed Fahmy and Bahar Mohammed were arrested at a Cairo hotel on December 29 on suspicion of broadcasting false news in the service of the black-listed Muslim Brotherhood.

"They have told us 'we were doing nothing more than our jobs'," Allan said of the men who have not been charged and face detention under Egyptian law stretching out to a possible two years.

During his time in Cairo's high-security Tora Prison, Greste can only be visited by family, lawyers and embassy officials and Australian diplomats have had repeated contact with the media frontman.

"The Australian embassy has been incredibly helpful ... they have been able to get in to see Peter.

"He doesn't have family there, so it has been a great lifeline for him," said Allan, who has spent the past three weeks travelling to Cairo but has not been able to see the men.

Friend and former colleague Fred Scott spoke of Greste's resilience.

"I've seen him cope with unbelievable levels of stress with great style and presence of mind and focus and I'm sure he's dealing with this situation in that same tough, steely fashion," Scott said.

But Greste's Brisbane-based parents Juris and Lois said their son would hate being confined.

"He loves his beaches, he loves his kite-surfing, bushwalking and he rides a motorbike to get around and we know that being cooped up anywhere for more than 24 hours is hell for him," Mr Greste told the gathering via video link.