Whilst after their defeat at Yorktown the British signed a Preliminary Peace in November 1782 to grant the US Congress independence, they also ceded the US its American territory to the "middle of the Mississippi River", and navigation "to the sea" that it had won in 1763 from the French. Nine months later, their conclusive treaty in September 1783 was signed after Spain's humiliating defeat at Gibraltar. The Americans then agreed to allow Britain to keep Canada to their north where they had not conquered at Quebec, and in a secret protocol they promised that in the event of a British reconquest of Florida, they would not to ally with Spain or France to contest any British acquisition there to their south. An important Canadian scholar has shown that regardless of the 1600s Stuart King land grants beyond the Mississippi River to the American colonies, Britain's primary motive in ceding its 1763 French territory to the Americans in 1783 was "to cheat the Spaniards."