The test dates back to 1865 and involves drivers memorising 320 routes, 25,000 street names and some 20,000 landmarks and places of public interest including museums, theatres, churches, police stations, schools and parks within a six mile radius of Charing Cross.
The routes through central London – which previously numbered as many as 468 – are contained within the Blue Book (there’s also a series of ‘Knowledge schools’ to help would-be drivers prepare for the test).
The test includes a written exam and a series of one-to-one interviews, known as appearances, in which the prospective driver is given start and finish points and expected to describe the shortest route between them. It is overseen by the Public Carriage Office, once part of the Metropolitan Police Force, but now part of Transport for London.
It was introduced by Sir Richard Mayne, First Joint Commissioner of the Metropolitan Police Service, after thousands of complaints were received about the lack of knowledge of London cabbies from visitors to the Great Exhibition in Hyde Park in 1851.
It apparently takes on average between two and four years to learn all you need to know to pass the test and you can often spot what are fondly known as ‘knowledge boys (or girls)’ riding scooters around the city with a clipboard attached to the handlebars as they learn what they need to know for the test.