In the spring of 1811, the French began using a code based on a combination of 150 numbers known as the Army of Portugal Code. Scovell cracked the code within two days. At the end of 1811, a new code called the Great Paris Code was sent to all French army officers. It was based on 1400 numbers and derived from a mid-eighteenth century diplomatic code ("Grande Chiffre") which added meaningless figures to the end of letters. By December 1812, when a letter from Joseph Bonaparte to Napoleon was intercepted, Scovell could decipher enough of it to read Joseph's explicit account of French operations and plans. The information gained proved vital to Wellington's victory over the French at Vitoria on 21 June 1813.