By Barbara Plett
BBC UN Correspondent
Roman Polanski's new political thriller The Ghost, which is opening in the UK, is about a former British prime minister who is threatened with being hauled in front of the International Criminal Court for alleged war crimes.
Pierce Brosnan's character was inspired by Tony Blair
The title refers to a ghost writer roped in to craft the memoirs of this ex prime minister, Adam Lang. But it is the ghost of Tony Blair that haunts the fictional Mr Lang, with references to Iraq, the "war on terror", and a much too cosy relationship with the United States.
The author of the book on which the film is based, Robert Harris, has said he was inspired at least in part by anger at Mr Blair's policies, and media reports of calls for the prime minister to face war crimes trials.
But how realistic is the film?
Could Mr Blair, or any other British prime minister, be within the reach of the long arm of international law?
In one respect, yes. The international criminal court, or the ICC, offers no protection for heads of state or government, serving or former.
After that it gets more complicated. First the court has to determine if the crime falls within its jurisdiction, and the threshold is very high.
In the film Adam Lang is accused of ordering an operation to kidnap four British citizens suspected of links to terrorism. They are picked up in Pakistan by British special forces and handed over to the CIA, which tortures them. One dies.
This may be a crime, say legal experts, but probably not on the scale of a war crime, or crime against humanity, the two categories under which Mr Lang is being investigated.
For the ICC to prosecute charges of torture, unlawful transfer or wilful killing, they must be committed as part of a policy that is executed on a wide scale.
"With the ICC what we're looking at is a government or regional organization that has sat down and said we're going to do 'x' against civilians or non combatants, and we're going to kill them in a systematic way," says Professor David Crane, the former chief prosecutor of the Special Court for Sierra Leone.
Anti-war protesters wanted Mr Blair prosecuted by the ICC
"It has to be a government policy to do harm to human beings that don't have a right to be harmed."
In the film the charge of rendition is bound up with the wider question of the Iraq war, with protestors against that war besieging Adam Lang's house.
This is close to fact: The ICC prosecutor was so inundated with complaints about Britain's role in the 2003 invasion and occupation that he conducted an investigation.
But, unlike in the film, he concluded there was not a case for trial.
While there had been wilful killings and inhuman treatment, he said, the number of incidents was comparatively small. Nor was there evidence of a policy by the British government to deliberately target civilians, or of civilian death and destruction clearly excessive of the military advantage achieved.
He also noted that national courts were dealing with the relevant Iraqi cases, which brings us to another key point missing from the movie: what about the British justice system?
In the film it is the ex British foreign minister who hands the incriminating dossier to the international court, saying his hand was forced because the government refused his private demands for an inquiry.
A swift launch of an ICC investigation then follows.
That is unrealistic, says Christian Wenaweser, president of the assembly of states that have ratified the Rome Treaty which set up the court.
"The first thing the prosecutor would still do (in the movie) is go to the British authorities and say look here's the information I have, what have you done, or what do you intend to do about it," says Mr Wenawaser.
"So even if they had previously refused to do anything about it, he would still give them the chance to do something now. That would be the first step. It would never play out the way it does in the film."
The drama also has Adam Lang - holed up in a villa in Martha's Vineyard - decide to stay in the United States for fear of arrest if he returns to Britain.
Technically this is a feasible scenario. As a state that has ratified the Rome Treaty, Britain would be obliged to arrest anyone for whom the ICC had issued a warrant, although it had not yet for Mr Lang.
The US has not ratified the treaty so it is not similarly obliged. However some legal experts are sceptical that Washington would protect such a high profile fugitive from justice, no matter how close an ally.
So the film is probably not an accurate depiction of what could happen today. But Richard Dicker, the director of the international justice programme at Human Rights Watch, hopes one day it may be.
"The landscape on which the ICC is applied is very uneven, specifically that the leaders of the more powerful states are much less vulnerable to being charged than the leaders of weaker states," says Mr Dicker.
"What's exciting about the film is that you see the ICC, representing international justice, going after the former prime minister of a permanent member of the Security Council."
What the film does do is chart a course through the dense thicket of international law on war crimes and renditions, making them understandable. That has educational value, says Mr Wenaweser.
"I don't think the film is accurate in every detail, but by and large I think the law is reasonably well represented and presented," he says.
"On balance I would say that it helps the larger public understand how international criminal justice can work."