Keira Knightley stars in Gavin Hood's thriller as Katharine Gun, the British whistleblower who leaked classified documents intended to strong-arm the U.N. Security Council into backing the 2003 U.S. invasion of Iraq.

While railing at TV news coverage of Tony Blair's double-speak concerning his position on the George W. Bush government's intention to invade Iraq in 2003, British intelligence translator Katharine Gun, played with the requisite impassioned principles by Keira Knightley, fumes, "Just because you're the prime minister doesn't mean you get to make up your own facts." With administrations on both sides of the Atlantic having lost the trust of their people, that line got a huge laugh at the Sundance premiere of Gavin Hood's political thriller, Official Secrets.

This is the kind of recent history lesson that tends these days to acquire more texture as a limited-series cable drama. Hood (Eye in the Sky), his co-screenwriters Sara and Gregory Bernstein and a seasoned ensemble of Brit stage and screen pros deliver a straightforward, solidly old-fashioned slice of real-life espionage, journalistic and legal intrigue that gets the job done in engrossing, clear-eyed fashion even if it lacks much in the way of stylistic verve. The cast alone should guarantee an audience, though how eager Brits or Americans will be to revisit this still-raw episode remains to be seen. Especially so soon after the thematically related Vice.

The story of an ordinary woman whose moral backbone gave her the courage to act in a potentially ruinous manner, the film is also a cautionary tale that continues to resonate today — about governments getting mixed up in international conflicts for the wrong reasons and with unrealistic forecasts. The elevated death toll on both sides speaks for itself. Likewise, the failure ever to find conclusive evidence of weapons of mass destruction or of ties between Iraqi dictator Saddam Hussein and al-Qaeda — the stated impetus for rushing headlong into the global blunder.

If the densely detailed two-hour drama arrives at a somewhat anticlimactic conclusion in the courtroom — a fact underlined by handing the soft coda to secondary characters — then there's the rub of sticking to the truth.

Gun has been working for two years at the Government Communications Headquarters (GCHQ), not far from her home in Cheltenham, England, when an email lands in her inbox from a division chief at the U.S. National Security Agency, outlining shady tactics to be employed in the push to go to war with Iraq and urging U.K. cooperation. The communication authorizes an eavesdropping plan on delegates from member countries of the United Nations Security Council, in particular those considered swing votes in the resolution necessary to launch the invasion. The language of the email and its blackmail objective are an unequivocal violation of global diplomacy. Gun secretly copies the classified document and passes it to a former colleague now involved in anti-war activism.

Given that we all know her effort to obstruct the path to war was unsuccessful, the film moves quickly to the complexities of going public with the damning information, at the same time that massive numbers of Brits are rallying in protest against being dragged into the conflict. But the majority of the drama chronicles the protracted fallout from Gun's impulsive decision, both in personal terms and in its embarrassment for the U.S. and British governments.

While Hood is a capable director he's no Alan J. Pakula, although enjoyable echoes of All the President's Men run through scenes at the offices of daily U.K. broadsheet The Observer, right down to the Deep Throat underground car park delivery of the incriminating document into the hands of reporter Martin Bright (Matt Smith). Convincing pugnacious editor Roger Alton (Conleth Hill) to run a story about an email that proves difficult to authenticate requires the combined legwork of Bright, his war-correspondent colleague Peter Beaumont (Matthew Goode) and volatile Washington reporter Ed Vulliamy (Rhys Ifans), whose CIA source confirms that the agency was bypassed in the plan.

The film's chief interest is in the behind-the-scenes drama in Britain. But the point is made that Bush ended up hurriedly sending bombers in to blitz Iraq even without the U.N. resolution, and that U.S. television networks, obviously caving under pressure, dropped plans to interview Bright once the story broke and was promptly discredited as a smear campaign by The Drudge Report. That makes it unsurprising that Gun's story is a minor footnote in this country.

When the investigation into the leak at GCHQ intensifies, placing her colleagues at risk, Katharine steps forward to confess. This opens her up to charges of breaking the Official Secrets Act, while her Muslim husband Yasar (Adam Bakri), a Kurdish-Turk, risks deportation. With GCHQ making threats via Scotland Yard, Katharine seeks help from a human rights law firm headed by Ben Emmerson (Ralph Fiennes), a shrewd strategist who clearly admires her spirit.

Despite being the pivotal figure in this sprawling scenario, Katharine gives Knightley disappointingly limited opportunities for interesting character shadings, mostly hitting the same notes of feisty indignation and speak-truth-to-power fortitude. Moments when she reveals her vulnerability are a welcome variation, becoming a young woman in over her head, positively shredded as the implications for Yasar become clear.

Fiennes could do this role in his sleep but he brings his usual probing intelligence, while Smith and Goode as always are agreeable presences but can't do much to make their colorless characters memorable. (Smith gets one big speech in which Bright expresses his humbled gratitude to Katharine that comes off as, well, big and speechy.) Ifans gets more mileage by going large, with liberal doses of profanity and the disheveled look of someone coming off a five-day bender. Hill has amusing moments as the hot-tempered editor, and there are sharp scenes with Jeremy Northam and Tamsin Greig in smaller roles.

The movie looks polished enough, and editor Megan Gill weaves in plenty of news clips from the era, with key figures like Bush, Blair, Colin Powell and White House press secretary Ari Fleischer in a particularly wormy bit of no-comment evasion. However, Hood's slightly underpowered approach is evident in how heavily he leans on Paul Hepker and Mark Kilian's high-intrigue score to fuel tension and suspense.

Venue: Sundance Film Festival (Premieres)
Cast: Keira Knightley, Matt Smith, Matthew Goode, Rhys Ifans, Adam Bakri, Ralph Fiennes, Indira Varma, Conleth Hill, Tamsin Greig, MyAnna Buring, Hattie Morahan, Jeremy Northam, John Hefferman, Monica Dolan, Jack Farthing, Peter Guinness, Kenneth Cranham, Angus Wright
Production companies: Classified Films, Clear Pictures Entertainment, in association with Silver Reel

Director: Gavin Hood
Screenwriters: Sara Bernstein, Gregory Bernstein, Gavin Hood, based on the book The Spy Who Tried to Stop a War: Katharine Gun and the Secret Plot to Sanction the Iraq Invasion, by Marcia and Thomas Mitchell
Producers: Ged Doherty, Elizabeth Fowler, Melissa Shiyu Zuo
Executive producers: Mark Gordon, Matt Jackson, Sara Smith, Gavin Hood, Claudia Bluemhuber, Anne Sheehan, Hugo Heppell
Director of photography: Florian Hoffmeister
Production designer: Simon Rogers
Costume designer: Claire Finlay
Music: Paul Hepker, Mark Kilian
Editor: Megan Gill
Casting: Kate Dowd
Sales: Sierra/Affinity

112 minute