Universally known as "black cabs" (even though many of them now come in other colors), the traditional big black London taxicabs are as much a part of the city's streetscape as red double-decker buses, and for good reason: the unique, spacious taxis easily hold five people, plus luggage. To earn a taxi license, drivers must undergo intensive training on the history and geography of London. The course, and all that the drivers have learned in it, is known simply as "the Knowledge." There's almost nothing your taxi driver won't know about the city. Partly because of lobbying efforts by the black cab industry, companies such as Uber have yet to make significant inroads into the London market, although the battle is ongoing.
Hotels and main tourist areas have cabstands (just take the first in line), but you can also flag one down from the roadside. If the orange "For Hire" sign on the top is lighted, the taxi is available. Cab drivers sometimes cruise at night with their signs unlighted so that they can choose their passengers and avoid those they think might cause trouble. If you see an unlighted, passengerless cab, hail it: you might be lucky.
Fares start at £3 and charge by the minute—a journey of a mile (which might take 6–13 minutes) will cost £6–£9.40 (the fare goes up 10 pm–5 am—a system designed to persuade more taxi drivers to work at night). A surcharge of £2 is applied to a telephone booking and £2.80 for journeys that start from the Heathrow Airport taxi ranks. At Christmas and New Year, there is an additional surcharge of £4. You may, but do not have to, tip taxi drivers 10% of the tab. Usually passengers round up to the nearest pound.
Minicabs, which operate out of small, curbside offices throughout the city, are generally cheaper than black cabs, but they are less reliable and less trustworthy. These are usually unmarked passenger cars, and their drivers are often not native Londoners, and do not have to take or pass "the Knowledge" test. Still, Londoners use them in droves because they are plentiful and cheap. If you choose to use them, do not ever take an unlicensed cab: anyone who curb-crawls looking for customers is likely to be unlicensed. Unlicensed cabs have been associated with many crimes and can be dangerous. All cab companies with proper dispatch offices are likely to be licensed. Look for a small purple version of the Underground logo on the front or rear window with "private hire" written across it.
There are plenty of trustworthy and licensed minicab firms. For London-wide service try Lady's and Gent's MiniCabs, or Addison Lee, which uses comfortable minivans but requires that you know the full postal code for both your pickup location and your destination. When using a minicab, always ask the price in advance when you phone for the car, then verify with the driver before the journey begins.