Quentin Tarantino recently admitted that Inglourious Basterds was hard work and has taken over as the most challenging of his career.

The cult movie director began drafting the script for the bloodied action movie over a decade ago and altered it several times over the years before completion last summer. “This is the toughest film I’ve ever made. It’s my Mount Everest movie. Kill Bill was hard, but this was harder,” Tarantino stated.

The 46-year-old says he drew inspired for the storyline from a “f**king cool” movie from the 70s. He explained to Loaded magazine: “I got it from a 1978 spaghetti western called Inglourious Bastards. It was about a bunch of guys fighting in Germany and were condemned to be court-martialed, when their prison convoy gets attacked by Nazis. They escape, so they have to find a way out. They try and get to Switzerland - a neutral country - but they have to battle their way through Germany first. It’s just a really f**king cool story. It was so cool that I wanted to come up with an equally cool film.”

Quentin’s version of Inglourious Basterds opens in the US on August 21.