Xu Lei, scriptwriter [Photo provided to China Daily]

Commenting on his script, Lee says: "Xu first wrote a story that had some 70,000 Chinese characters. If I had shot a film based on his first draft, it would have taken six hours of screening.

"But I was very impressed by Xu's writing skills. His language and rich knowledge of Chinese history made the final script very attractive."

The director reveals that the most appealing part of the script is the emotional connection between the raiders.

After revising the script nearly 20 times in two years, the shooting began in a 6,000-square-meter area in Beijing, where special effects were done by an international team.

Interestingly, despite the overseas technical support, Xu has a different view on Chinese filmmakers' foreign ambitions.

"If you take a look at (Hollywood) blockbusters, very few cast Chinese as protagonists. In some sense, it means Chinese culture has yet to be recognized globally," he says.

The deeper he studies cultural differences, the more he thinks that Chinese movies should still focus on the domestic market, Xu says.

When asked if his next plan is to take the director's chair, as fellow novelists Han Han and Guo Jingming have done, Xu gives a sly smile.

"It's a very painstaking job. I'm afraid I can't afford the stress," he says, adding that Lee wakes up at 4 am to start work.

It might be too early to predict how far the writer will tap into the showbiz industry. His nervousness and worries are obvious.

On a recent Sina Weibo post for his "book fans", he wrote: "I'm writing for a film for the first time. If there are shortcomings, please don't blame me too much."