Official Secrets is a based-on-fact story that, as far as I can tell, is reasonably close to what actually happened. Catherine Gun, a translator who works for British Intelligence, leaks a top secret memo that suggests the upcoming 2003 invasion of Iraq is illegal. Gun gave the memo to an activist friend who gave it to a journalist. Once the story became front page news, Gun confessed, and she was charged with breaking the Official Secrets Act.
Gavin Hood (Eye in the Sky) wrote the screenplay with Gregory and Sara Bernstein, and they manage to keep things from getting too confusing. The script is clearly on Gun's side, which will bother you or not, depending on your own take. Keira Knightley is in serious mode ... the film itself is pretty serious ... her presence makes us care about what happens to Catherine. There is a level of tension throughout, although the conclusion is almost a shaggy dog story (not that Hood could do anything about it ... it's what actually happened). The movie is solid, no more, no less, a decent outing if nothing else.
The cast includes Ralph Fiennes and a variety of "That Guys": Indira Varma, Matthew Goode, Matt Smith, Rhys Ifans, Tamsin Greig, Conleth Hill.