Created in 1791, Ordnance Survey (OS) is the official National Mapping Authority for Great Britain. It creates a range of maps for all sorts of activities. Dr Gareth Moore is the best-selling author of The Ordnance Survey Puzzle Book, The Mindfulness Puzzle Book, The Times World Atlas Puzzle Book, The Mammoth Book of New Sudoku, Stay Sharp! and many more puzzle and brain-training books.