staving Roger Mills:

> ISTR reading that London cabbies have to go through a course that
> involves practically memorizing the London street guide/map. But at
> least the streets have names !!� No doubt GPS has simplified matters
> for them.

Ah, yes, The Knowledge. A retired Black Cab driver explained this to me 
recently. They have a set of routes to learn, which at first seem quite 
bizarre and arcane ("Go from A to B via X, Y and Z"). As they learn more 
and more of the set routes, they start to fit together, until they are 
able to work out the best route from anywhere in London to anywhere else 
in London in any traffic conditions (except, apparently, south of the 
River late at night). Cabbies apparently have enlarged hippocampuses as 
a result of learning all this.

The Knowledge is the qualification to be a Black Cab driver. It's 
possible to drive a minicab without it, but minicabs are only licenced 
for pre-booked journeys. Only Black Cabs are licenced to accept hails.