Public Carriage Office - The Knowledge:
All licensed taxi drivers in the capital must have an in depth knowledge of the topography of London, 'The Knowledge'. For would be All London or 'Green Badge' holders, this means that they need to have a detailed knowledge of London within a six mile radius of Charing Cross. This is based on 320 routes (or 'runs') as set out in the Public Carriage Office "Guide to Learning the Knowledge of London" (the 'Blue Book'). They also need to know the places of interest and important landmarks on the route and within a quarter mile radius of both start and finish points.