The black taxi cab driver is required to be able to decide routes immediately in response to a passenger's request or traffic conditions, rather than stopping to look at a map, rely on satellite navigation or ask a controller by radio. Consequently, the 'Knowledge of London' Examination System, informally known as 'The Knowledge', is the in-depth study of London street routes and places of interest that taxicab-drivers in that city must complete to obtain a licence to operate a black cab. It was initiated in 1865, and has changed little since.

It is the world's most demanding training course for taxicab-drivers, and applicants will usually need at least 12 'Appearances' (attempts at the final test), after preparation averaging 34 months, to pass the examination.

Course details

The 320 main (standard) routes, or 'runs', through central London of the Knowledge are contained within the 'Blue Book' (officially known as the 'Guide to Learning the Knowledge of London'), produced by the Public Carriage Office which regulates licensed taxis in London. In all some 25,000 streets within a six mile radius of Charing Cross are covered along with the major arterial routes through the rest of London.

A taxicab-driver must learn these, as well as the 'points of interest' along those routes including streets, squares, clubs, hospitals, hotels, theatres, government and public buildings, railway stations, police stations, courts, diplomatic buildings, important places of worship, cemeteries, crematoria, parks and open spaces, sports and leisure centres, places of learning, restaurants and historic buildings.

The Knowledge includes such details as the order of theatres on Shaftesbury Avenue, or the names and order of the side streets and traffic signals passed on a route.

There are separate shorter courses, for suburban London, with 30 to 50 'runs' depending on the sector.

Be warned, about 70% of people who start the Knowledge give up before their appearances. The Knowledge is incredibly demanding.

"Knowledge boys"

During training would-be cabbies, known as 'Knowledge boys' (or girls), usually follow these routes around London on a motor scooter, and can be identified by the clipboard fixed to the handlebars and showing details of the streets to be learned that day. Taxi-driver applicants must be 'of good character', meeting strict requirements regarding any criminal record, then first pass a written test which qualifies them to make an 'appearance'. At appearances, Knowledge boys must, without looking at a map, identify the quickest and most sensible route between any two points in metropolitan London that their examiner chooses. For each route, the applicants must recite the names of the roads used, when they cross junctions, use roundabouts, make turns, and what is 'alongside' them at each point.