“I didn’t want to do a police show because I’m really bad at saying those kind of lines, which you have to do when it’s procedure. I really avoided police shows,” he revealed.
But River is different: “They hadn’t written a ‘police’ show really. That’s just an excuse for it.”
The six-part series, which also stars Lesley Manville and Last Tango’s Nicola Walker, sees Stellan, 64, portray brilliant police officer John River. He is “visited” by dead and dying victims and killers from unsolved murder cases – figments of his imagination that enable him to discover the truth behind the crimes he investigates.
Stellan said: “You could say it’s a crime story on the surface, but it’s really more about a person’s breakdown or his psychological status. It’s a mixture of the danger of illegal actions and psychological vulnerability.”
The actor, who has starred in films including Thor, The Girl with the Dragon Tattoo and alongside Meryl Streep in Mamma Mia!, struggled to adjust to the pace and style of TV.
“One of the things is that when you make a film it’s either a big Hollywood film and then you know the machinery, or it’s an independent film, and then the director is the creative centre.”
“But here they changed director and that was extremely frustrating to me, because a new director comes in and then you have to show him what he has to do. It’s not my job.”
He also had trouble adjusting to the speed of TV. “They shoot so much every day. I used to do two minutes maximum per day. Here it’s like eight minutes or so.”
However, the Swedish actor said a decline in the film industry was good news for television. “All the sort of more adult character-driven films that attracted good writers, good actors, good directors they don’t exist any more because there’s no distribution system, they don’t sell enough popcorn,” he explained.
“So all that talent has now gone to television more and more – and what you will see is that television will also have to change their production methods a little.”
And it seems Stellan plans to shift to the small screen: “I’ve said ‘no’ to a lot of television, and a lot of cop shows. But they’re doing so much good television now. If you look at The Wire or True Detective, there’s fantastic stuff out there now, so I’ll probably do more of it.”
As John River, the actor got more exercise than he bargained for; he had to film chase scenes on foot.
He explained: “You run for 10 seconds, 20 seconds in that film. Well, that means that you run for an entire day when you’re shooting it, and that hurts. I should read scripts properly. If there’s a running scene I should just say ‘no’.”
BBC1’s River begins at 9pm on Tuesday