JARHEAD director Sam Mendes confesses he was seduced into making the Gulf War movie, after producers sent him a clever marketing gimmick.

The Oscar winner came clean at a recent screening for the film, which stars Jake Gyllenhaal and Peter Sarsgaard.

He says, "They sent me the book in a marine rucksack as a ruse, so I'd read it. And when I opened the rucksack, sand fell out of it.

"Then when I read the book's opening line, it was something like: 'I opened my marine rucksack and it was full of sand.'"