Ordnance Survey is the official mapping agency of Great Britain.
First formed by order of George II in 1746 to help keep the rebellious Scots in order. They have been making the world's finest maps ever since.
They are particularly important during the various Unpleasantnesses that afflict our nation. During the Normandy landings for instance they provided around 120 million maps.
Not only that but they help enormously when a chap gets lost in the grounds of whatever country house he may or may not be visiting.