Oranges and lemons? – if you are a London black cab driver, or studying to be one, then you will know what we are referring to. A-Z maps are extensively referred to during the two to four years it takes for applicants to successfully complete and pass ‘The Knowledge’. That’s a working knowledge of the 25,000 streets, 320 routes (runs) and 20,000 points of interest within a six mile radius of Charing Cross. The oranges and lemons? – well that’s the A and B road colours of course.