The Knowledge: a cabbie's perfect mental picture of where everything in London is, except you, when you really need a cab. Hoping to fix that: Uber, entering its testing phase today.
Commanding a high-end fleet of Merc S-Classes and BMW 7's, this on-demand pickup service will send a black-suited chauffeur directly to you in minutes flat, while still remaining hyper-competitive with black cabs, to the point that the black cabs probably ought to keep an eye on their girlfriends. Just open the app (or SMS your locale), and it'll drop a pin either where you are, or where you want to be picked up from; you can follow the nearest driver's progress as he wings his way towards you, complete with an ETA, so thank god for that ceasefire.
The whole deal including tip's auto-charged to your credit card, and you get to rate your driver, with the company keeping close tabs on the worst performers and the best, who they'll presumably give a badge to -- just not a green one.