“I was thinking, Who could play this fellow?” Edward Berger says. “You know, we go to some pretty dark places.”

They do. Ballad of a Small Player, the director’s follow-up to Conclave, closes in on a gambling addict as he courts self-destruction amid the nauseating decadence of Macao’s supercasinos.

“He’s a fraud, a liar, a thief and, of course…”

“And I straight away thought, ‘I know the right man!’” Colin Farrell ventriloquises with a hearty chuckle.

And we’re away. You don’t so much interview Farrell as curate his conversation. A professional down to his neat fingertips, he gives you, in 20 minutes or so, enough material for a smallish book.

He was like this as cocky whippersnapper, but, now closing in on 50, he has a great deal more to talk about. Childhood in suburban Castleknock. Promising years as a young soccer player. The audition for Boyzone. Training at the Gaiety School of Acting. Local breakthrough in the TV series Ballykissangel. International breakthrough in Joel Schumacher’s Tigerland. A period in rehab for addiction to painkillers and recreational drugs.

I observe that one or two journalists have, cynically, as I too am about to, used Ballad of a Small Player as a route into conversation about that difficult period. This is, among other things, a film about addiction. “Lord” Doyle, protagonist of Berger’s blaring, deliberately alienating picture, cannot stop himself throwing good thousands after bad. He also guzzles lakes of champagne and sucks trainloads of Cuban cigars (despite not much caring for either).

So is gambling addiction an entirely different business from substance abuse?

“No, I don’t think it could be classified as an entirely different business when you see the consequen