Pay a visit to London and a black cab will probably be one the first things you will see. The London taxi drivers are almost as famous as the black cabs in which they drive, this is mainly due to their in-depth knowledge of London and ability in taking their occupants to their desired destination amid the congestion and the chaos that you often find when travelling through London's streets. London taxi drivers go through stringent training to obtain their licence, they need to pass 'The Knowledge', a test which is amongst the hardest to pass in the world, and has been described as 'like having an atlas of London implanted into your brain'.