This was the only way that the scene, in which he is violently throttled by a kidnapper, would look as realistic as it did, says the 54-year-old actor.
"Maybe it is because the actors who played the kidnappers all grew up watching me on the screen, but they didn't strangle me hard enough at first. As soon as I started struggling, they would stop.
|Mr Wu Ruofu|
"So I told them that if I really couldn't take it, I would just let go and stop fighting them, and that they shouldn't stop strangling me until I did that. We really put in a lot of effort to express the suffering of the real-life characters," he tells Life in an e-mail interview.
During filming, he also spent 10 hours each day shackled painfully in real metal chains (fake chains would break apart as soon as he tried to free himself) and was confined to just 1 sq m of space.
He never talked about the case. I think he has already said everything that he wanted to say about it a decade ago when he spoke to the police.
ANDY LAU on the real kidnap victim,
actor Wu Ruofu, who has a small role in the film
Still, whatever challenges Lau faced during the shoot probably came nowhere close to the ordeal that China actor Wu Ruofu must have felt during his real-life kidnap in 2004, on which this film is based.
The abductors were sentenced to death in 2005, a year after the incident, but it is clear that Wu is still haunted by the memories of how he was snatched by kidnappers outside a bar in Beijing and held captive for 21 hours - he had rejected the offer to play himself in this movie. Instead, he takes on a small supporting role as a cop.
Lau says: "Director Ding Sheng told me that it was too much for Wu to live through the whole experience all over again as the victim, so he took the part of the police inspector who helped save his life instead. It was his tribute to his rescuer.
"He never talked about the case. I think he has already said everything that he wanted to say about it a decade ago when he spoke to the police.
"But during the filming, we would observe his facial expressions and reactions to try and gauge his thoughts, to see if we were playing this as close to real life as possible. If he looked too deep in thought and his mind was elsewhere, we knew that our observations were accurate."
Now that the film is set for release, Lau hopes that it can help provide Wu with a sense of closure.
"Wu Ruofu is a remarkably strong person, but the experience still haunts him. I hope he can put the past behind him after this movie.
"We actually changed the Chinese character of Wu's last name, with the new 'Wu' meaning 'me'. So to save Mr Wu is also to save me.
"The title thus symbolises the saving of Mr Wu from the abductors, but also the liberation of the real Mr Wu."