Only this time around, he has three new movies - , , and - slated to open on the same day: February 19, the first day of the Lunar New Year. Does he see that as a career milestone? Koo pauses for seconds, and says, "Is that my personal record? I don't look at it that way. It doesn't matter how many movies I have around this time. The most important thing is that the audiences have fun."

The Lunar New Year turns out to be one of Koo's favourite times of the year. "It's one of those rare occasions where you can sit down with the entire family to watch a movie. When I'm paying a New Year call to my relatives, I'd suggest going to the cinema too. It's a festive period for all. Watching movies, going to the flower markets, singing karaoke and playing mahjong: these are all options."

Combine that sentiment with the lucrative box office potential of Lunar New Year - according to the HK Motion Picture Industry Association, a quartet of Chinese-speaking titles notched more than HK$118 million in that slot last year - and you understand why Koo relishes the holiday period.

"But that's not a factor when I choose to accept an offer," he says.

For those in the media, it's common knowledge that Koo is a reticent interviewee. And the already tense atmosphere is exacerbated by his long-time manager Ronnie, who continually cuts off questions not directly concerned with the one movie Koo is there to promote. Which means you won't be reading much about or in this piece.

Ironically, of the three festive films Koo is starring in, - the one he's here to talk about - stands out as the only project that didn't begin as a Lunar New Year offering. "When I agreed to this, I didn't know that it would end up opening then," he says.

A spin-off of the popular TVB drama series that ran for two seasons in 2003 and 2013, has added two stars - in Koo and singer-actress Sammi Cheng Sau-man - to the original cast headed by Francis Ng Chun-yu and Julian Cheung Chi-lam. The action is set in Hong Kong and Britain, with Brighton and London providing scenic backdrops.

And while there are three pilots and one flight attendant among its six protagonists, the movie is more romance than aviation drama. Koo remembers enjoying watching the television series. "It's about the joy and sorrows in the careers of airline pilots and flight attendants. People are curious about these professionals because they get to fly to so many different places around the world."

For those who long for Koo to replicate his magic on the small screen - he emerged from a career-shaping spell at TVB from the mid-1990s to early 2000s, and is still contracted to make a 40-episode series that he's been putting off since - will come as some solace as the actor shares an onscreen romance with television mainstay Charmaine Sheh Sze-man.

"She's a very professional actress with a lot of experience," says Koo of his co-star. "Although there are three storylines in this film, we managed to grasp the feeling of romance in the limited time we were given. It was difficult, but I think she did very well."

The occasion also marks Koo's reunion with Wilson Yip Wai-shun and Matt Chow Hoi-kwong, the experienced director-scriptwriter pair behind (1999), starring Koo and Francis Ng. For a change, Yip and Chow are taking on co-directing duties for the new film.

"Actually, I think it's the first time Yip has made a romance," says Koo, who has forgotten that he also starred, alongside Miriam Yeung Chin-wah, in the director's 2002 rom-com, .

"He was quite nervous before the shoot, but eventually found that it is an easier task than he had imagined."

It's a small industry these days, and no one would be shocked to learn that Matt Chow also directs , the Sandra Ng Kwan-yu comedy vehicle - and a sequel, in spirit, to last year's popular - to which Koo lends a hilarious supporting role, this time as a fitness trainer.

Given that the actor has starred in all four Raymond Wong Pak-ming-produced movies released between 2009 and 2012, it's hard to feign surprise at Koo's titular role in yet another Wong ensemble comedy. Co-directed by Wong and Herman Yau Lai-to, is a Cantonese adaptation of J.B. Priestley's classic British play.

Koo downplays his productive output by way of a general assumption. "The truth of the matter is that the quantity of actors working today - not just in Hong Kong but in Asia in general - is on the smaller side. It's the case for both male and female actors," he says.

Judging by his recent reappointment as ambassador of the Hong Kong International Film Festival, the latest edition of which kicks off on March 23, he may have a point about the shrinking pool of acting talent. It's almost a mundane footnote to add that Koo's fourth film of 2015, education drama , also opens that week.

"Well, there are other actors who are very prolific too," Koo says. "I'm just one of them. It's no big deal. I do hope there'll be more actors who can establish themselves and give everyone more options."

As possibly the highest-profile Hong Kong actor to have never been named best actor at the city's annual film awards, Koo says he will "leave that to fate" and won't strive for more attention-seeking parts.

"They wouldn't come up just because I wanted them to," he dismisses my inquiry with more than a hint of impatience.

While there is always the dilemma that we may be feeding the beast by offering the reluctantly famous star this cover story, it would border on professional negligence to ignore this incredibly prolific phase of his career.

The question has to be asked: is there any role that you would say no to?

"None."

Which means that you'll be taking up any new challenge that finds its way into your hands?

"Yes."

In the uncomfortable silence that follows, one thing is obvious: Koo is not going away.