This frame from Louise Osmond's superb ITN/C4/Nova documentary "The Search for the North West Passage" brings to mind an artistic technique beloved of renaissance masters such as Caravaggio. Chiaroscuro, or in its most developed form Tenebrism, enhances the drama of an image through extreme contrasts of light and darkness. The dramatised scenes in this documentary are a tour de force. In this scene, shot in the officers saloon of the Cutty Sark, Anthony Gardner makes a very convincing Sir John Franklin. I have however noticed three minor mistakes. If anyone would like to suggest what they are then please go ahead. I'll add my answers in a couple of days.