Reviewed by GREG KING Director: Gavin Hood Stars: Kiera Knightley, Ralph Fiennes, Matt Smith, Matthew Goode, Rhys Ifans, Adam Bakri, Jeremy Northam, Conleth Hill, Tamsin Greig. This is quite a tense, topical and thought-provoking drama based on the true story of Katherine Gun, a whistle blower who tried to stop the invasion of Iraq by leaking an official memo to the press. Gun (played here by …