Note to King Lear, 3.3.8: "There's a division betwixt the dukes"

Gloucester tells Edmund "There's a division betwixt the dukes; and a worse matter than that . . . " The "dukes" are the Duke of Albany, the mild and sensible husband to King Lear's eldest daughter, Goneril, and the Duke of Cornwall, the fiery husband of Regan, King Lear's second daughter. The emerging quarrel between the two dukes has been mentioned in both Act 2, Scene 1, line 10 and Act 3, Scene 1, line 19.

The "worse matter" is that advance forces of the King of France, Cordelia's husband, have already gained a foothold in English ports. They are coming to avenge the injuries done to King Lear. Thus England faces the prospect of both a civil war between the two dukes and an invasion by the French army.

Gloucester goes on to tell Edmund that he has received a letter about the imminent French invasion and that the letter is hidden in his private study. The letter is hidden because it is evidence that Gloucester knows and approves of the plans of the King of France and his Queen, Cordelia. Therefore Regan and the Duke of Cornwall would consider the letter proof of treason. [Naturally Gloucester's evil bastard son, Edumund, will use all this information in order to incriminate his father and take his place as the Earl of Gloucester.]