Matt Damon plays Chief Warrant Officer Roy Miller in Green Zone (dir Paul Greengrass, 2010), a fast, high-octane romp through the dusty streets and half-destroyed palaces of post-invasion Iraq.

Once the bombing strikes ended in 2003 the question should have quickly turned to the pressing issue of weapons of mass destruction (WMD) and where they were hidden. News crews from around the world staked out their patches in the Green Zone, only occasionally venturing out into Baghdad's grimy suburbs and preferring to cover press conferences organised by US military heads.

It's in the suburbs that the movie starts. Miller and his team make visits to city locations in an effort to uncover WMD stashes but repeatedly come up empty-handed. When he complains, Miller is silenced by a senior commanding officer and by Clark Poundstone (Greg Kinnear), a tightly zipped-up and besuited Washington bureaucrat with an agenda to push.

Frustrated, Miller seeks help from Martin Brown (Brendan Gleeson), a tubby CIA operative in an ill-fitting brown suit who is on a collision course with military spooks, who are trying to protect the fiction WMD embody. So when Miller gets some intelligence about the location of "high-value target" General Al Rawi (Yigal Naor), he takes it to Brown and not to Poundstone.

Getting the intelligence happened by chance. Working in the field, Miller is approached by an Iraqi citizen named Freddy (Khalid Abdalla). Freddy tells him there is a meeting of senior Baathists happening nearby. Miller takes his team to the house. They enter it and capture three Iraqis but Al Rawi escapes. Thinking he is onto something, Miller is naturally disappointed when a rival group of US soldiers choppers in, abducts the captives, and leaves him bleeding from the nose.

Undaunted by the unseemly scrape, Miller attempts over the next few days to get to the bottom of the puzzle. If WMDs are absent every time they move in on a target site, where did the intelligence come from?

He asks Washington Post journalist Lawrie Dayne (Amy Ryan). A senior official gave her the information, she replies. Didn't anyone verify it, asks Miller. No, she says; when you get raw information from such a source you don't ask questions.

Working with Brown, Miller works out that Poundstone had visited Jordan at the same time as Al Rawi. They had met to discuss WMD. Putting two and two together, Brown and Miller face up to the fact that the lies go right to the top. This insight is confirmed when Poundstone raids CIA HQ in the Green Zone and confiscates Miller's field intelligence.

Everyone is trying to find Al Rawi, but not all of them for the same reason. Some want to get him to talk - did the US lie about WMD? - and others want to prevent him from talking. The chase sequence that ends the film takes us into the suburbs once more. These are the same suburbs that the Iraqi tribal heads will argue about in the conference room in the palace under the "leadership" of the US-backed government head. Poundstone, watching the bickering, can only scratch his head.

As for Miller? He's just put back on the road to continue his work.

In 2010, the bombings in Iraq have slowed to a trickle thanks to negotiations that could have taken place years earlier. That they still occur is one reason this film had to be made.