The Avengers
      November Five (3x6)
      
      : 
      Michael Dyter, the newly elected MP for South-East Anglia is shot shortly after making his acceptance speech in which he had threatened to expose a major scandal involving the government.  Steed knows that the subject of this was the recent theft of a nuclear warhead near London.  So was Dyter killed to keep him quiet, and if so, by whom?