The episode again touches upon the theme of immunity from justice despite the war that aims to champion such noble ideals as British law and order. Much of the episode's historical content was inspired by the invention of the bouncing bomb and the Dambusters raid of 1943, as portrayed in the film "The Dam Busters". Writer Anthony Horowitz planned his story to "shadow" one aspect of the bomb's development; the episode depicts a group of scientists experimenting with a mechanism to put backspin on the bomb. The test sequence was designed to replicate the actual tests, including a depiction of the official cameraman, which allowed them to add in archive footage. Another historical reference in this episode is the bombing of the Sandhurst Road School, in Catford, South East London, on 20 January 1943, in which 38 children and six teachers were killed, and some 60 other children and adults were injured. Filmed: March–April 2006