 Consequently, the "Knowledge of London" is the in-depth study of a number of pre-set London street routes and all 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 to pass at least twelve "appearances" (periodical one-on-one oral examinations undertaken throughout the qualification process), with the whole process usually averaging 34 months, to pass.