Transport for LondonThe Knowledge
How long it takes to become a licensed taxi driver depends on whether you want to be an All-London driver or a Suburban driver.
London or the suburbs?
All-London drivers - also known as Green Badge drivers - need a detailed knowledge of London within a six mile radius of Charing Cross.
All-London drivers have to learn 320 routes (or runs). They also need to know all the landmarks and places of interest along the runs.
It takes between two and four years to pass the All-London Knowledge. Once you are licensed you can work anywhere in the Greater London area.
Suburban
Suburban drivers (also known as Yellow Badge drivers) can choose from London's nine suburban sectors. They must know between 30 and 51 runs in detail. They also need to know all landmarks and places of interest on the runs.
It takes around two years to become a licensed Suburban taxi driver. Once qualified, you can only work in the sector you are licensed for.
You can find out more about the two licences on the Licence types page.
The Knowledge makes your brain grow
Doing the Knowledge makes your brain bigger, says research by the Wellcome Department of Imaging Neuroscience.
Researchers scanned the brains of 16 London taxi drivers who had spent an average of two years learning the Knowledge. They found the cabbies had a larger hippocampus - an area associated with memory - than control subjects.
Find out more at the Wellcome Trust website.
