To celebrate her historic visit to Bletchley Park, the home of the Codebreakers of World War II, Her Majesty The Queen has issued a challenge to schoolkids: break a book of war-time ciphers.
The Codebreakers worked in secret throughout World War II, intercepting and decoding encrypted German communications to aid the war effort. General Dwight D. Eisenhower described the information obtained in this way as of 'inestimable value,' claiming that it was directly responsible for saving thousands of British and American lives.
Now, children from throughout the UK are invited to get a taste of the sort of work carried out at the Park with a codebreaking challenge of their own.
The Queen has issued a code book - dubbed the Agent X Code Book Challenge - which contains a sample of the sort of encryption system used by the Government Code & Cypher School at Bletchley Park during the war, and seven messages encrypted using the scheme.
The challenge, which is aimed at UK residents aged 13 to 16, is to decrypt these messages. The seventh is the key: it contains a question which must be answered in order to enter the contest.
Those who work out the secret code required to unlock the secrets of the book are asked to e-mail the answer - in unencrypted form - along with their full name, age, date of birth, parent or guardian's name, telephone number, and full address to email@example.com before 1800 on Thursday the 18th of August.
From the correct entries, a single winner will be picked to receive what is described as 'a small prize'.
If you fancy having ago, the code book can be downloaded in PDF format.