John Buchan 
The Courts of the Morning 

The Courts of the Morning is a 1929 adventure novel by John Buchan, featuring his character Sandy Arbuthnot. The prologue is narrated by Richard Hannay, so the novel is sometimes included in Buchan's Hannay series. The action is set in Olifa, a fictional country on the west coast of South America.
When Sandy Arbuthnot's friend John Blenkiron discover that a charismatic industrial tycoon is plotting to rule the world from his base in the small South American country of Olifa, Sandy leads a revolution to scuttle the plot and allow the Olifans to decide their own fate.