Remember when the Coen brothers opened Fargo with the legend “This is a true story” and it turned out to be fiction? Roger Donaldson’s new heist thriller The Bank Job seems to operate on the reverse principle. A press release says it was “inspired by” the 1971 robbery of a London bank, suggesting a certain amount of fiction. But a full year ago the UK Observer reported that screenwriters Dick Clement and Ian La Frenais drew on a “deep throat” informer familiar with the hushed-up case to “incriminate high-ranking police officers, the secret service, politicians, and a prominent member of the Royal Family.”

A more recent story in the UK Telegraph neatly sorts the established facts from the conspiracy theory. On September 13, 1971, thieves tunneled from an adjacent storefront into the bank’s basement safe-deposit section and made off with £3 million in cash and jewels. A ham radio operator happened to catch some of their walkie-talkie communications and contacted the police, who tracked down the location of the robbery. It was too late to catch them, but police broadcast recordings of the culprits in hopes of someone identifying them. After four days of heavy media coverage, the government issued a “D order” prohibiting any further press stories on the robbery.

The screenwriters’ Deep Throat turns out to be a man named George McIndoe, listed as a producer on the film, who claims that he met two of the robbers. McIndoe’s story is that the robbers were indirectly sponsored by MI5, the British intelligence service, which was after sexually incriminating photos of Princess Margaret being held in a safe deposit box by the revolutionary Michael X. The movie argues that Gale Ann Benson, the daughter of a conservative MP whose body was found in a shallow grave on the grounds of Michael X’s Trinidadian commune in 1972, was in fact an MI5 spy trying to get the goods on Michael. And, just for good measure, I suppose, Clement and La Frenais also have the robbers stumbling on ledgers of police payoffs, a discovery that makes them the target of violent reprisals from the cops.

The movie opened in the UK last week and hasn’t forced the royal family to abdicate. But having turned the story into an entertainment instead of a muckraking documentary, the writers will probably get a lot more mileage out of the material and face a lot less scrutiny. Another story, in the Daily Mail, revisits Princess Margaret’s wild social life; oddly, it states that Margaret is never named in the movie, though the print I saw has heist meister Jason Statham gaping at the photos and exclaiming “That’s Princess Margaret!” Could there be two different cuts of the movie, one for the U.S. and another the UK?

I could go on, but I hear black helicopters outside and must head for the basement.