It's a remarkable story, told with slick thriller flair, focusing increasingly on the interdependence of its subjects, who chose personal morality over political rhetoric, with isolating results.

Schirman, a young Israeli film-maker, has gotten hold of an extraordinary espionage story and - how could he not? - turned it into an undeniably gripping documentary.

Depending on your perspective, Nadav Schirman's troubling documentary is either a story about heroism and friendship or a study in extreme treachery and bad faith.

Here lies an intriguing story that calls to mind John Le Carré at his murky best, yet what we are given is the self justification and propaganda.