If you walk around London long enough, you will see people on motor scooters equipped with clipboards. Who are these people?

They are aspiring London cabbies, learning the tangled network of roads they will have to negotiate in a city that dates back to the Roman Empire. This is a place where street names change unpredictably; just down the block from where I work Clerkenwell Road becomes Theobald's Road. And the grid street plan is an alien concept.

Taking a book of street maps along when you venture outside your neighborhood is considered normal. The standard work is the "A to Z", also referred to as the "A to Zed" (We have two of them).

The process of learning London's streets in order to qualify as a cabbie is called "getting the knowledge."