Cheung explains the casting: "I think he's a very obvious candidate to play the role. He looks very much like a hero in chaotic times. Ching-wan is actually a very nice guy in real life, but he has a ferocious look." She adds that Lau was her only choice throughout the lengthy pre-production process of the 80 million yuan (HK$96.7 million) production that traversed China - from Anhui and Shenyang to Shanghai and Hong Kong.

"In a war like that, people like us would be dead after five days," Law chimes in, referring to himself and Cheung, the husband-and-wife team who won widespread acclaim with the 1960s-set (2010). "But Ching-wan looks like he would do just fine."

For the uninitiated, Lau has been putting his sometimes scruffy, often manic screen persona to good use since he slipped into the part of a vengeful stockbroker in TVB's iconic 40-episode drama series (1992). Its over-the-top moral conflicts set around the stock exchange resonated with viewers during its recent TV rerun.

What followed for Lau is a career that includes 16 best actor nominations at the Hong Kong Film Awards, two wins (for in 2007 and this April), as well as a best actor award for his part in (2011) at Taipei's Golden Horse Film Festival.

Lau's stature as a film star was cemented through his influential collaborations with Johnnie To Kei-fung and Wai Ka-fai for the production house Milkyway Image, which the two founded in 1996. The Milkyway connection has inadvertently painted Lau as an actor who excels at epic crime thrillers over the years.

His memorable roles as mental patients in the art-house favourite (2007) and the recent didn't help, either.

"I like to play characters that are less conventional, less 'normal'," says Lau. "Some directors also find me a bit neurotic."

With baggage like that, Lau may be forgiven for savouring the anomaly of , a romance. "People think that I became famous from cops-and-robbers flicks, but no," he says, grinning mischievously. "At the start of my career, when I went from TV to films, nobody could have predicted that my breakthrough would come with a romance movie."

The actor is referring to his heart-breaking performance opposite Anita Yuen Wing-yee in (1993), the Derek Yee Tung-shing film that was named best picture at the Hong Kong Film Awards and went on to become one of Hong Kong cinema's most beloved romances.

But Lau is given a reality check when asked to name his last romance movie. "Was it ?" His voice trails off. He is referring to a film directed by Yee and starring Cecilia Cheung Pak-chi that was released in 2003, more than 12 years and 20 movies ago.

"Ching-wan said he'd made only two or three romance movies previously. He said this might be his last," adds director Cheung.

All these have made an occasion. Loosely based on the true-life stories of Fang Daolong and Chen Yuerong - later known as Charlie Chan and Lee-Lee Chan, parents of action star Jackie - Cheung's film was written when the director looked to tell the stories of her mother's generation of immigrants after her death in 2003.

While Lau can identify with the character's situation - his own father fled to Hong Kong on foot; his mother on boat, before they met each other in the city - the actor is especially taken by the fact he's acting for a female director on this project.

"I've made a lot of films directed by men, including romances, and it's my theory that these films represent romances between the directors and their lead actresses. A director picks an actress and I embody him in the film. The romances I made - , - were more driven by the female leads," he says.

"So when Cheung Yuen-ting picked me, it became a love story between me and her to a certain extent. In , both protagonists come from similar backgrounds and had tragic experiences - her husband was killed in a bombing raid and his wife by disease. They go through parallel stories before they meet."

In spite of his tough exterior, the actor proves himself to be quite an emotional person at heart. When I tell Lau that I spotted him taking a paper tissue from his wife after receiving his best actor prize at this year's Film Awards, he offers me a misty-eyed monologue.

It revolves around the accidental death of veteran cameraman Chan Kwok-hung on the set of the Jackie Chan movie back in December; the cameraman had worked on all three films that Lau starred in.

"I seldom take photos with my phone, but during an on-location shoot for a car chase in , I took a photo of [Chan] alongside all the cameras and equipment on an open-top jeep," Lau recalls.

"Later, after the accident, I remembered that I had taken this photo. When I went on stage that day, the most poignant part was that we hadn't talked much during the shoot, but he was a very responsible member. This person existed in the process, but you didn't get a chance to say much to him. It's only afterwards that I realised we lost him."

Lau appears to have a tendency to freeze a scene in real life and then recall it in vivid detail much later. As our discussion touches on a soon-to-be-released police thriller, which is titled in Chinese, Lau doesn't only recall the early negotiation he had with its creative masterminds but emphasises that he was "surrounded by them" at the meetings.

Likewise, as his train of thought turns to , Lau doesn't just tell me how he got to work with Yee (previous co-starring opportunities on a Taiwanese TV series; then a casual chat at a bar) but he also remembers the name of the venue where they had their chat (Jazz Club in Taipei).

When I finally ask Lau, for simple fact-checking purposes, whether he prefers the name "Sean Lau" or his Chinese name "Lau Ching-wan", which are both evenly used among his movie's credits, he says, "Now there's another story behind this.

"When I was making the film in 1993, there was this fellow actor called Michael Chow Man-kin. One time, we were really bored waiting around on the set, and I asked if he could give me an English name. I wanted it to be really simple, short and easily pronounced. He suggested 'Sean', but added that I didn't look like a 'Sean'. I said, 'So what?'"

Lau hadn't used that name since but, inexplicably to him, somewhere along the line someone picked it up and "Sean Lau" has been regularly adorning giant billboards over the years.

"I think Lau Ching-wan is good enough," the actor concludes. You can say that again.