McG believes the most crucial part of directing a movie is getting the casting right.

The filmmaker is currently promoting his new movie This Means War, which stars Reese Witherspoon, Tom Hardy and Chris Pine.

The director explained why the romantic action movie needed a cast of strong actors to make it work.

This Means War tells the story of two best friends, who happen to be top secret agents. When they find out that they are in love with the same woman, they battle each other with high-tech surveillance and advanced tactics to win her affections.

“I believe that 90 percent of directing is casting, so I wanted to get together a group of talented people and you’ve got Chris and you’ve got Tom and you’ve got Reese,” McG told Cover Media at the London premiere of the film. “The film mixes a lot of tone – it’s an action picture and there’s a lot of comedy and there’s a lot of romance – and it’s all over the place and to make that satisfying in the end it required the deft touch of the three actors. And dare I say a fourth actor, Chelsea Handler, who is out of her mind.”

McG also revealed how the two leading men’s cultural differences brought an interesting element to the character development.

He explained that they deliberately let British thespian Tom Hardy keep his accent because it added credibility to his story.

“They’re very different and continental – Tom has such a decidedly British energy and Chris is American to the core, and that’s an interesting rivalry and we picked that up in the picture,” he said.

“We discussed it [Tom’s accent] beforehand and there was a bit of a back story that he’s come from the MI6, so it worked well for the character.”

– film-news.co.uk