Calais became an English possession in 1347, when Edward III captured it during the Hundred Years War and the English rule was formalized in 1360 by the Treaty of Bretigny. The town and its surrounding area, known as the Pale of Calais, measured about 120 square miles and were heavily fortified against incursions from France. Calais served as an important port for English goods, particularly wool, entering the Continent. Calais eventually fell to the French in January 1558, in the reign of Mary I. Calais was formally lost in the reign of Elizabeth I under the Treaty of Troyes.
Although the last holdings in France were lost to the English crown in Mary’s reign, Elizabeth and all the following English monarchs continued to keep “France” in their title until it was formally given up by George III in 1801. The French symbol of the fleur-de-lis was also removed from the Royal Arms at this time.