Although all actors know that when they sign a film, the fee they get is not only for their dates to shoot the film but also to help market it, most still look at promotions as a favour. This is where the real professionals, the marathon winners, score over the runners-up.

And Shah Rukh Khan is a marathon runner. He loves promoting his films and says it's like, "Bidaai for your daughter. A film is like your baby. Promoting it is like the bidaai after you've shot and completed it and you have to let go of it." When his Fan was on release, after winding up long promotional sessions at YRF Studios, he went next door to a TV channel at 1am with a spring in his step. Even at that hour, admirers awaited him since word had spread that he would be there for a one-on-one for a popular entertainment show. Whether the box office divorced itself from the film or not, SRK played his part in the bidaai with unending energy.

Twenty-three years his senior, Amitabh Bachchan has also picked up the market requirements with trademark professionalism and participates with full gusto in the promotion of his films. The current beneficiary of AB's enthusiasm is Te3n , the mystery thriller inspired by Korean cinema.

"We don't have the money to promote it the way big films are today," Amitabh said bluntly. So, novelty had to make up for it. It was AB's idea to top up the usual media interactions with a closed door session that had only a handful in the audience and no cameras. It was filmed exclusively for the Te3n team for its promotions.

The closed door chat had Amitabh, producer Sujoy Ghosh and director Ribhu Dasgupta in conversation with Vishal Dadlani who is as popular for his anti-Right tweets as he is for the music he composes with partner Shekhar Ravjiani. Vishal-Shekhar have a special equation with Sujoy who chose them for his first film, Jhankaar Beats .

I'm not sure why Vishal was asked to moderate the conversation because the man who can conduct a two-hour musical show for a large audience without missing a beat, turned ice-cold playing interviewer. Sujoy too, was out of his depth as the conversation had to be in Hindi. I also think Sujoy is carrying his casual look too far. Okay, he didn't turn up in shorts, but even for a session that was going to be filmed, he came unshaven, wearing loose crumpled jeans and slippers.

But Amitabh Bachchan made up for everybody else and came up with several nuggets of information. One was about Ekla chalo re , the Tagore composition he sang for Vishal-Shekhar in Sujoy's Kahaani four years ago. It's a song that Bengali singers like Kishore Kumar and more recently Shreya Ghoshal have recorded with native fluency. And AB was only aware that someone as monumental as Kishoreda had sung it before him.

"In fact," revealed Amitabh, "there's one little portion which I've sung in Hindi." The original idea was to record Amitabh's version of Ekla chalo re with only that stanza in Kishore Kumar's voice. But the makers of Kahaani ran into "copyright problems" with Kishoreda 's rendition, so it had to be the baritone all the way. And he did just that bit in Hindi.

The shooting of Te3n had Sujoy's trademark of guerilla shooting all over it. Remember how he'd got Vidya Balan to go into the real crowds during Durga Puja to shoot the climax of Kahaani? They've done it again with Te3n . "There are no sets in my film," says director Ribhu. "We shot all over Calcutta on actual locations."

When a shot of Amitabh on a scooter couldn't be filmed because of the crowds that had gathered, the actor decided that instead of putting it off to another day, they should attempt it another way. So they hid the cameras and other equipment where the public wouldn't get wind of the shoot and Amitabh was dropped off kilometres away from the site. Amitabh pulled a cap low over his forehead to cover most of his face and nonchalantly rode the scooter around Calcutta without attracting attention, zooming into the frame of the camera as required and zooming off before anybody caught on.

Astonishing that a 73-going-on-74 could be so enthused about work? I dare say he does it because he just enjoys his work and the company of his young colleagues so much.

One must mention that AB won his first National Award in 1990 for Agneepath when Kangana Ranaut was three years old. In 2016, AB wins the award for best actor the fourth time and Kangana for best actress for Tanu Weds Manu. In other words, he's still out there competing alongside kids who'd just about learnt to walk when he won his first National Award.

"What can I say?" he said, bending a whole foot to talk to me. "I've just been very fortunate."

Bharathi S. Pradhan is a senior journalist and author