Not many people have who are caught on film drunkenly screaming their heads off at a football game are immediately offered the lead in a film – but then, Alexander Skarsgard isn’t just anyone.

“Oh god!” the True Blood and Legend of Tarzan actor laughs, embarrassed by the memory. “I was at a football game, my team Hammarby from Stockholm were playing and I was, em, merrily chanting!” he says euphemistically, indicating that some drink may have been taken. “I was screaming at the crowd and they were shouting back – I didn’t realise that people were filming!”

And people were watching – including John Michael McDonagh, the acclaimed director of Calvary and The Guard. The video shows Skarsgard embodying a much louder, playfully aggressive side than his usual sensitive onscreen presence; a machismo that lent itself perfectly to one of the lead roles in McDonagh’s upcoming dark comedy, War On Everyone.

Skarsgard and Michael Pena star as two corrupt cops in Mexico City who blackmail and frame criminals for their own benefit. But when they cross someone with more power than they, things get dangerous – and not a little bit weird.

Skarsgard, son of Swedish actor Stellan Skarsgard, said he was a huge fan of McDonagh’s work, and was thrilled to be cast as the nihilistic, foul-mouthed Tommy.

“I’d seen both The Guard and Calvary,” says the 40 year old actor, “and so even before I opened the script, I was stoked. I was really excited about it. And then I opened it and on the first page our characters are chasing a mime, then we hit him and steal his cocaine. I was like, ‘I’m in!’ From page one I was riveted, it was so un-PC and wild. It’s a crazy ride!”

Skarsgard’s character Tommy is racist, misogynistic and hilariously unhinged in the way that only McDonagh can write (the possible exception being his similarly humoured brother, Martin). But as the film reveals itself to be a dark satire of American cop films and corrupt justice systems, it does move from irreverent to terrifying. Skarsgard say he enjoyed playing with the tonal shifts and complex themes.

“It’s very dark and quite funny but it was also a bit of a challenge,” he reveals, ”because toward the end of the movie, it gets darker and more personal, and that was interesting for us to navigate. It’s important that the audience care about the characters.”

The film itself was a departure for the actor, who started filming War On Everyone straight after starring in The Legend Of Tarzan, David Yates’ reboot of the classic character. Released on DVD this month, the film marked a dream come true for Skarsgard.

“I had really prepared for that role my entire life,” laughs Skarsgard. “I used to pretend to be Tarzan as a kid, I loved Tarzan! My Dad used to show me the old movies when I was a kid, so of course I was very excited about the project. I also thought it was such a smart take on the classic tale. It felt like an update, but also a really new and important story. But it was also fun, every morning it was like entering an amusement park.”

Though he was a lifelong fan, Skarsgard wasn’t too disappointed when he didn’t get to give Tarzan’s epic yell onscreen, instead settling for it merely being heard in the distance.

“I think it’s a tough one because if you remember the old movies, it works because of the tone of the movie. But it’d easily look cheesy or comedic if you did that in 2016! It’s more dramatic and haunting just to hear it through the jungle and see the reaction on his enemies’ faces – they know they’re being hunted.”

Despite starring in the dark fantasy series True Blood, Skarsgard wasn’t used to working with the level of CGI and special effects required for Tarzan – and found some of it slightly awkward.

“There’s a scene where I’m nuzzling a lion, which was actually a guy, a dancer from South London wearing grey pajamas!” he laughs. “I’d just met him that day and then we were down on all fours nuzzling. And when there’s a lion running across the Savana, that was two guys holding a cardboard cutout. It was so much fun to watch the movie with all the effects and remember how ridiculous it felt doing it, and to see this awkward moment with a dancer turning into this really emotional moment with an animal.”

Skargard has yet to watch The Legend of Tarzan with his father, and admits he is anxious to see his reaction.

“He’s the one critic I get nervous about!” he says. “He introduced me to film – I used to sit next to him on the couch and we’d watch films together, and now we sit together and watch each other’s work. It feels very special.”