What is the exposition of "The Destructors" by Graham Greene?

Theof a
short story often includes the setting, backgrounds of the characters, and a reference to any
events that took place prior to the beginning of the story.

• The setting of the story is the eve of the August bank
  holiday in England, sometime after WWII, likely the late 1940's or early 1950's. The characters
  live in a working-class neighborhood called Wormsley.


• The backgrounds of the characters  is that they are all
  young males in a group that calls itself the Wormsley Common gang.  The latest recruit is
  Trevor, who goes by the nickname "T"; he has been raised in a higher class than the
  other boys, but his family has recently fallen in society due to his father's comedown from
  architect to clerk.  T challenges Blackie to become the...