GCHQ are back with a new collection of head-scratching, mind-boggling and brain-bending puzzles that will leave readers pondering for hours.

For those who found themselves occasionally stumped with the first book, there will be even more starter puzzles to get those brains warmed up. Puzzle aficionados, meanwhile, can test themselves to the limit with an 'Even Harder' section.

In celebration of GCHQ's over 100-year legacy the puzzles will be structured around vignettes of its history direct from the archives. providing exclusive snapshots into the organisation that keeps up all safe, making it a book to treasure.