Cao hailed Liu as best qualified to portray the late premier.

"Liu has spent almost his entire career playing Zhou. I think he is more than competent to direct the film," says the 76-year-old writer.

The film mainly tells the story of the events that occurred on June 9, 1973, when Zhou returned to Yan'an, the revolutionary base of the Communist Party before the founding of New China in 1949.

Zhou's bodyguard Gao Zhenpu was invited to work as a consultant on the film, as he had been accompanying Zhou from 1961 until his death.

"On that day (June 1973), Premier Zhou stayed in Yan'an for 22 hours during which he only managed to rest for less than 3 hours," Gao reminisced at a news conference for the film at the Diaoyutai State Guesthouse in Beijing on Dec 15.

"As an observer, I was touched by the intimate relations between Zhou and the people of Yan'an. I believe that the film will show the love between the Party and the people, and help us immortalize the patriotic spirit of the revolutionary pioneers."

The film is being produced by the China Culture Media Group and China Great Wall Asset Management Corporation with support from Zhou's niece Zhou Bingde and other family members, senior makeup artist Wang Xizhong, scriptwriter Zhai Xiaoguang and some experts in Party history.

How to maintain the appeal of a story spanning just 22 hours was the greatest challenge for the new director. Liu says the whole group spent a great deal of time discussing the storyline.

"We wanted to break away from the single-line narrative of the original book and include retrospective historical stories from the perspectives of people like Gao.

"The stories involve the germination of the 'Yan'an spirit' and how it was passed down from generation to generation," says Liu.

"The film will be well worth the wait," Liu adds.