Jake Gyllenhaal underwent hefty physical and emotional training for his role as a renegade young cop in David Ayer’s ‘End of Watch’.

After five months spent pulling night shifts with the LAPD preparing for his role in David Ayer’s gritty cop drama End of Watch, Jake Gyllenhaal is sure of one thing: “I don’t think I could ever do a police officer’s job for real,” he sighs.

“The only similarity I can see between an acting job and a real police officer’s work is the ability to observe human behaviour. Obviously the stakes are a lot higher for a police officer,” says the actor who estimates that he went on more than 50 ten-hour shifts with co-star Michael Pena as they prepared for a 22-day shoot in which they attempted to emulate the bond between cops whose lives literally depend on one another.

“Just watching those police officers, it was interesting to see that we do share a real similarity in that both our jobs require an ability to interpret behaviour and sometimes even mimic, depending on where they were. That was fascinating to me.

“Only in that sense do I think I might be okay at the job. But the other aspects – like fearlessness and all the other technical stuff – I don’t think I could do that nearly as well as the guys on the streets. But ultimately I had to feel like I could. And I definitely did, rightfully or not, feel like I was as close to a police officer as an actor could get while we were shooting the movie.”

The Los Angeles police department doesn’t always pull out the red carpet for every actor wanting to fake-believe the life-and-death drama that is an everyday reality for those cops whose beats include the toughest gangland areas, and it was thanks to director/writer Ayer that they were able to pull those strings, having established a trust from his earlier cop films including Training Day, Dark Blue, Street Kings and S.W.A.T.

Gyllenhaal sounds almost nostalgic when he describes the long hours spent preparing for End of Watch: “We did ride-alongs with the LAPD two or three times a week from 4pm to 4am and then we did tactical training twice a week for six-hour sessions progressing on to using live ammunition and training together. It was very intense. And then we did fight training, sparring, every morning five days a week working at a dojo in Echo Park that Dave’s [Ayer] best friend owns, and then we’d rehearse in between that, and the rest of the time Mike and I just spent together. I hardly saw the majority of my friends during that entire time because Mike and I were always working on something.”

At the end of the day, Gyllenhaal is smart enough to know that none of his own personal relationships can compare to the bonds between cops prepared to literally take a bullet for their partner: “Without a doubt I do have friendships like I have with Mike’s character in my own life but it’s a different scenario where your lives are legitimately threatened every moment you get out of that car; it’s a different type of friendship which is inexplicable to those who’ve not been in that same scenario and I think it can’t be. There’s no way. Unless I was with one of my close friends and we had to go to war together, and then that question would be asked and I think then I would probably have to say that there are some people I know ‘Yes, they would [lay down their life for me]’, but I don’t live in that scenario so it’s hard to say.”

Admittedly, not all the cops assigned to Gyllenhaal and Pena were happy to have two movie stars along for the ride: “Occasionally we’d be put with people who we knew were giving us the run-around and we’d just get the fuck out of there as quickly as we could; we just knew that it was bullshit.

“But over time, because of David’s relationship with law enforcement we started to get more and more inside and started to gain trust. We were never obviously doing what they were doing but we were with them every time in whatever scenario they were in.

“If you’re on a ride-along, you sign away your life. You’re in there with them, and you’re their responsibility as well as the scenes they had to show up at. We realised very quickly that this was double the burden for them but, after a while, we were able to know what to do to make them feel more comfortable so they didn’t have to baby-sit us as much. But we were never doing what they were doing, ever,” says the actor who watched a man literally bleed to death on his very first ride-along as well as witnessing a brutal domestic violence fight between two gay men. “The whole experience was literally life-changing for me.”

With his striking big blue eyes and chiseled leading man features, Gyllenhaal, 31, could have easily been just another pretty boy but, determined to escape type-casting, he took on a string of diverse roles with Jarhead, Zodiac, Love and Other Drugs and Source Code, as well as signing on for big bucks blockbusters Prince of Persia and The Day After Tomorrow.

Perhaps the most defining moment of his career, thus far – was his role as Jack Twist in Brokeback Mountain’s tale of forbidden love between two cowboys; nominated for an Oscar together with co-star Heath Ledger in what would become one of the most celebrated films of 2005.

Next up he plans to co-star with Hugh Jackman in Boston kidnap drama Prisoners although a start date is not yet set in stone.

Increasingly taking an interest in producing, Gyllenhaal was given an executive producer title on End of Watch only after the film was completed.

“We made the movie for US$7 million and shot it in 22 days and just the nature of how we shot it, and all of those things, there were a lot of favours being asked for and I started acting as a producer while doing the acting and also in the post-production process. We were all in it together and the whole movie had that spirit. And by the end of that, Dave called up and said he wanted to give me an executive producing credit for all the work I’d done. That was actually one of the most exciting days of my career so far. It was something I really earned and I’m really proud of.