What is the importance of the "diamond" in the novel, King Rat?

For several months prior to the start of the novel, the rumor that one of the prisoners has a 4-carat diamond has circulated through Changi. The King manages to find out who has the diamond. With the help of Peter Marlowe, who acts as his interpreter, the King goes to a great deal of trouble to put together a complicated and dangerous deal to sell the stone to a Chinese trader. The deal for the diamond is the largest that the King has ever attempted. When it is over, he believes that the massive amount of money he receives has made him invincible. A few days later, however, the war ends and the money becomes worthless, leaving the King with nothing.