Speaking at the world premiere of his directorial debut, The Water Diviner, which depicts the aftermath of Gallipoli, he said one of the unexpected challenges of sitting in the director's chair was the paperwork that went with it.

There was a surprising volume of legal documents to go through to finance the film, he said.

"I think the count is 1400-and-something at this point in time, and you've got to be very careful that your t's are crossed and your i's are dotted and that everything is put in place right, because the liability factor can come back and bite you in the bum," Crowe said.

With plans to direct Anh Do's 2010 autobiography The Happiest Refugee next, he said it was a matter of waiting for The Water Diviner to prove its mettle at the box office.

"Here's the risk," he said. "This movie [The Water Diviner] has to work commercially or it's back to the end of the line, buddy. So if it works commercially we can take the template of how we finance this one and apply it to the next one."

Crowe said he hopes to begin working on Anh Do's story, in which the Vietnamese-born comedian describes his family's days at sea while fleeing to Australia, early next year. "It's another Australian story that hasn't been told, another sort of area that hasn't been opened up and it's got so much heart in it," Crowe said.

For now, all focus is on The Water Diviner. As the second war adventure to get its world premiere at the State Theatre in recent weeks - following the Angelina Jolie-directed WWI biopic Unbroken in mid-November - Crowe's story takes a step beyond Peter Weir's Gallipoli (1981) by moving into the years after the battle.   

On directing in general, Crowe said his experience in front of cameras since the age six and in lead roles for 25 years meant his path was easy in some respects. "I know the nature of film, I know its relentless nature. I know the respect you have to pay to your budget, to the assets you have on board, to the time that you have, so none of that is a surprising thing."

As well as directing, Crowe plays the lead role of Joshua Connor, a Victorian farmer who travels to Turkey in 1919 seeking his three missing sons – and closure.

It's a story that emerged from a single sentence in a letter by   Lieutenant-Colonel Cyril Hughes of the Imperial War Graves unit, who was working on the abandoned battlefield at Gallipoli. His letter said simply: "One old chap managed to get here from Australia, looking for his son's grave."

The letter was discovered by Melbourne writer Andrew Anastasios who, along with SeaChange and Rake writer Andrew Knight, saw enough in the line to spark an idea that became a feature-length screenplay which was picked up by Crowe.

Crowe took to the red carpet to launch The Water Diviner at the State Theatre on Tuesday evening alongside his two sons, Charles, 10, and Tennyson, 8. The cast present included former Bond girl Olga Kurylenko and Australian actors Jai Courtney, Jacqueline McKenzie and Dan Wyllie.

The moving, confronting story is as much about family and loss as it is about war - with care taken to present all sides of the story, including the Turks'.

Anastasios said of the film's broad perspectives: "It was important to do something about the commonality or the universality of the experience for people after the war, so not really a war story but more about the survivors of the war."

Actor Jai Courtney, who played Lieutenant-Colonel Hughes, said very little was known about his character. "It was up to me and Russell to find and develop and walk this balance between having this task, this really important job to do, but also find compassion for this guy [Crowe's character, Connor] who was completely a fish out of water and in the wrong place, and help him with his plight somehow."

Filmed between December and February across Sydney and South Australia - with McClaren Vale doubling for the Gallipoli peninsula - and later briefly in Turkey, it's an impressive, accomplished and challenging directorial debut by Crowe.

The Water Diviner is released on Boxing Day.