Taxicabs are regulated throughout the United Kingdom, but the regulation of taxicabs in London is especially rigorous both with regard to mechanical integrity and driver knowledge. An official report observed that: "Little however is known about the regulation by anyone outside the trade." The Public Carriage Office, who regulate and license taxis and private hire (commonly known as minicabs) was transferred from the Metropolitan Police to become part of Transport for London in 2000.

Only licensed taxicabs can pick up passengers on the street. London's Black cabs are particularly famous on account of the specially constructed vehicles and the extensive training course (the Knowledge) required for fully licensed drivers; unlike many other cities, the number of taxicab drivers in London is not limited. London's taxicab drivers are even well-known for having developed an especially big hippocampus, a region of the brain where, among other things, information about locations is stored.

London's black taxicabs - short for "taximeter cabriolets", that is, "cars with distance meters" - are a ubiquitous sight on the streets, and a common way to travel around the city in addition to the Tube and buses. In their favour, they're warm, comfortable and the drivers generally know where they're going, as they have to pass a rigorous test called "the Knowledge" before they can get their license to drive. The downside to the black cabs is that they're expensive, and unless you have very deep pockets there's no point using them for longer journeys across town. This situation has been exacerbated recently by the ex-Mayor of London Ken Livingstone's decision to let them charge more at night, since the drivers would often be reluctant to work at night.

Although the traditional London taxi is black, they now often come in a multitude of colours. Try looking out for their distinctive shape, that said, there are now newer, bigger, boxier models as well. If in doubt, look out for the orange "TAXI" light above the windscreen. If it's on, you can hail the cab. If not, you'll have to wait for another.

The London black cab is an icon of our city. Black cabs are extremely reliable, but rather expensive. The reason for this is because the drivers know so much about London. All drivers have passed "the Knowledge" which means they have studied and memorized 25,000 London streets within a six-mile radius of Charing Cross, proving they know the most direct route for your journey. These studies take about 2-4 years so it's rather like them having a university degree in 'London'.

The legendary black taxis of London seem to have been around forever, though nowadays not all the 23,000 black cabs in greater London are black, and a modernised streamlined version has been added to the "lumpy" old beasts. The bulging roofline of these taxis was originally designed to accommodate the height of bowler hats.

All taxis are wheelchair accessible and most have a variety of additional features to assist passengers. The fares charged are regulated, and with safety paramount all taxi vehicles and drivers must meet minimum standards . Licensed vehicles are subject to regular checks by the Public Carriage Office.

http://www.taxi-london.net/

The History

The Black Cabs' history goes back to the time of horse-drawn cabs which were called Hackney Cabs. The term comes from the French word haquenee referring to the ambling horses used to pull the original Hackney Carriages. The Hackney Carriage originated in London, England in 1625. The cabs still come under some of the old rules from the horse-drawn days. The Black Cabs are the only taxis that are allowed to pick people up from the street. There are also mini cabs in London, however they can only collect someone if they have made a prior arrangement by phone.

Before a taxi driver gets his Hackney Cab Licence he or she must pass a test called 'The Knowledge'. This is a difficult test and requires the cabbie to know the streets of central London like the palm of their hand. Mini cab drivers do not need to pass this test.
The Knowledge

Taxi drivers in London undergo a demanding and arduous testing of their knowledge of the city, its daily traffic patterns and the fastest routes between locations. Estimates suggest that gathering the basic understanding needed to acquire The Knowledge involves a full-time year of study, absorbing the information provided by street maps and travelling around the city itself.

The result is that drivers of official London Hackney Cabs are renowned for their detailed and intimate knowledge of London's streets and attractions. Strangely enough, scientific study has shown that possession and expansion of The Knowledge increases the size of the anterior and posterior hippocampi of the brain - the area that handles spatial memory and spatial navigation.

Compared with baseline controls and inexperienced cabbies, long-serving taxi drivers possessed considerable more developed hippocampi.

The Vehicles

There are currently 3 makes of vehicle licensed to ply for hire in London:

LTI (London Taxis International) - FX4 taxi, Fairway taxi, Fairway Driver taxi, TX1 taxi, TX2 Taxi & TX4 taxi.
Metrocab - Series 1 Metrocab, Series 2 Metrocab, Series 3 Metrocab & TTT Metrocab.
Eco City Vehicles - Mercedes Benz Vito Taxi.
All of these vehicles have to conform to the conditions  of fitness as set out by the PCO (Public Carriage Office).
http://www.taxi-london.net/