from the records of the colonial office and from the dead woman 's diary we learn that a certain young english nobleman , whom we shall call joan clayton , lady greystoke , was commissioned to make a peculiarly delicate investigation of conditions in a british west coast african colony from whose simple native inhabitants another european power was known to be recruiting soldiers for its native army , which it used solely for the forcible collection of rubber and ivory from the savage tribes along the congo and the aruwimi .