£2.2 with 336meters included, and by every next 168m you will pay additional 20p. But fares can be more expensive overnight and at evenings. Many of people have heard of Computer Cabs which actually means that you can order a cab via phone. You will pay £2 of booking fee plus the cost to get to you and plus your fare of course. Be aware that pre-booking can be only done by using a credit card.
Another concept of the London taxi is Zingo taxi which locates you by using the GPS to mobile phone system. By other words it means that black-cab driver gets in contact with you by mobile phone and then you can describe what is your exact location. For this service you will pay £1.6 fee which is calculated in the final price. Using Zingo taxi can be great idea at late night when it almost impossible to get a free cab, but if the service can't provide a vehicle for you (and that means one of the 1000 which they have working) you will be redirected to the computer cab service.
There is another cheaper version of black cabs and those are called minicabs. Minicabs however, have less knowledge in compare to the real black cabs drivers, but they offer cheaper service. However, they can be hired only by phone or from their minicab office. And for the price.. this kind of cabs don't have meters, so it's setup to fix the price before the start.
Another interesting thing in London is, if you're a woman and prefer to have a woman as driver you can hire so called ladycab, and the same goes for the gay and lesbian population, they can hire libertycabs.
London taxi - cab phone numbers:
Computer cabs phone number: 7908 0207
Zingo taxi phone number: 0870 070 0700
Minicabs phone number: 7387 8888, 7272 2222, 7272 3322, 8888 4444
Ladycabs phone number: 7272 3300
Libertycabs phone number: 7734 1313