Almost since writing was invented there has been a desire to hide some of what was written from prying eyes. State secrets, commercial information, love letters and much else have been considered too sensitive to be left around for others to read. The answer was to write the material in a code that was known only to those who were allowed to be in on the secret. Inevitably, as soon as codes were invented there was a demand for people who could break them and unlock potentially valuable secrets. Code-breaking calls for great reserves of ingenuity and guile. Have you got what it takes? This is where you find out. Pit your wits against some of the greatest code writers of all time and see whether you can penetrate their secrets.