For his latest role actor Jake Gyllenhaal stars opposite Michael Pena as a pair of LA hotshots working the toughest beat in town in cop drama End of Watch.
Directed by David Ayer, the man who wrote Training Day, the film is propelled by gritty action scenes shot by handheld and surveillance cameras, but grounded in the brotherhood of Gyllenhaal and Pena's characters, Officers Taylor and Zavala.
The two leading actors took time to bond on set and it was a lengthy process, explained Gyllenhaal.
He said: "It was forced at first, and had we had less time I think it would have felt forced, but we had so much time that we moved through that period of time of feeling forced into knowing that we needed each other.
"We were doing live ammunitions training, shooting with live rounds together and doing tactical exercises together, fight training where we were fighting every morning for five days a week and then we were on the streets with the police officers where we had to look out for each other.
“When they'd go run off and go chase a suspect or something was happening or we were in the middle of something, Michael and I had each other's back and that was a real situation, so all of those things created a friendship.
“We knew we were really friends when we started to fight, we knew that we had gone past the point of us being forced friends and into real friends. And that took two months.”
According to Gyllenhaal the real test of friendship is when you can tease each other.
He recalled: "There was a lot of bantering between us at the time because he was trying to get into really good shape, so we would all have these wonderful Mexican meals at Dave Ayer's house that his wife would cook, and we'd all sit around the table and Mike couldn't eat any of them.
"There was teasing all the time. I think that's what makes the movie good, is because true friends within the right context get to tease each other."
As well as a vigorous training process, the actors were put through a lengthy research period where they spent time shadowing real life officers in the field in order to help make their characters as realistic as possible.
"We had a special connection with a lot of these police officers because of David Ayer, our writer and director, who wrote Training Day, and wrote a lot of other really amazing cop movies. They knew that the goal was to make a real, a realistic portrait of what's it's like to actually be a police officer.
"And in that sense I think they were open to showing us who they really were."
- End of Watch is out now in UK cinemas.