Dominic Cooper takes on Saddam's son, and his double
Leaders from George W Bush to the late Osama Bin Laden are all rumoured to have had a political "double".
In The Devil's Double British actor Dominic Cooper plays one such doppelganger, as well as the man he was ordered to impersonate.
In 1983 Latif Yahia, a lieutenant in the Iraqi army, was forced to become the "fiday" - or double - of Uday Hussein.
Saddam Hussein and both his sons used decoys for important political occasions, or in situations where a bullet catcher might be needed.
Yahia, who eventually managed to escape Iraq with the help of the CIA, claims he stood in for Uday when addressing troops during the Iraqi invasion of Kuwait.
In the film, directed by New Zealand's Lee Tamahori, Cooper becomes both Uday and Latif in order to tell what he calls "an incredible story".
The use of political decoys is nothing new. During World War II, for example, both Hitler and Himmler were believed to employ them.
"It's a captivating idea," says Cooper. "The thought that a basically good man has to live every day with someone so hideous, and that he has no choice in the matter."
Much of The Devil's Double is based on Yahia's autobiography about his experiences, called I Was Saddam's Son.
Largely ignored prior to the invasion of Iraq in 2003, it has since sold more than one million copies worldwide.
Twenty years after he fled the country, its author says he is still affected by his experiences.
"I still have nightmares, still find it hard to get to sleep until the early hours of the morning," says Yahia.
"Every time I go into the shower, I see the physical scars on my body and think: 'Why did this happen to me?'"
Uday Hussein's international image was that of a playboy. But he was notorious for his abduction, rape and killing of young women and his torturing and murdering of opponents.
He even fell out of favour with Saddam after he killed the Iraqi leader's personal valet at a party.
That episode is depicted in The Devil's Double. But many more real-life events have been left out.
Had they been included, Yahia says, "it would be a horror movie, If we put in all the details, I don't think anyone would watch it."
"There are some extraordinary scenes of violence which actually took place and some of them are harrowing," concedes Cooper.
Yet the Mamma Mia! star insists they are justified in the context of the film's "glimpse of a gangster regime".
Cooper's biggest on-screen challenge was to make sure audiences could distinguish between the two very different people he was playing.
"It was terribly complex because of the doubling-up and because our technology budget was tiny," he says.
"I had to do the two roles simultaneously, on every shooting day. I would try and film Uday's part first, as his outbursts require so much emotional energy.
"Really, I had to use the differences between the men in the way they moved and spoke."
Both Cooper and his director insist the movie is a thriller, rather than a faithful biopic.
Critics so far have been divided over the results, though all agree this could be a breakthrough role for its 33-year-old star.
In its review, Empire magazine says the film is "a blistering, brutal Iraqi Scarface" and that Cooper is "fantastic - twice."
Yet Time Out's critic was less effusive, calling the movie "even more tasteless than its main character's gold 'n' marble palace".
Though it has been screened in such film festivals as Sundance and Cannes, there are no plans to show The Devil's Double in Iraq - mainly for security reasons.
Uday Hussein was killed by US troops in 2003 - much to the frustration of Yahia, who says he had wanted his former "employer" to answer for his crimes.
For his part, Cooper believes that the Husseins were "madmen" and "monsters" and deserved the fates that befell them.
"If there is one thing I am quite assured of, having filmed this movie, it's that they were right to get rid of Saddam Hussein and his sons," he declares.
The Devil's Double is out in the UK on 10 August.