Last year, GCHQ set a challenge to the public in the form of a cryptic Christmas card.

This year, they went one step further and wrote a whole book full of puzzles. The answers to most of these puzzles are in the book, but there are one or two challenges that they haven’t revealed the solutions to…yet.

Penguin Random House and GCHQ went on a hunt for Britain’s smartest puzzler, and this quest began with The GCHQ Puzzle Book, in which the first part of The GCHQ Puzzle Book Competition appeared.

Like last year’s competition, this one had various parts to it, and these required both puzzle-solving and codebreaking skills. As you proceeded, the instructions for entering the competition became clear.

The competition closing date was 28 February 2017.

THE COMPETITION HAS NOW CLOSED AND A TIE-BREAKER HAS BEEN ISSUED TO THE FINALISTS. THE WINNER WILL BE REVEALED IN DUE COURSE…

 Even though the competition has now closed you can still get yourself a copy of The GCHQ Puzzle Book and test your wits against the nation’s best codebreakers!