Mysterious Black Cab

I was walking on the High Street last week when I saw a unusual sight: a bona fide black cab going up the street. Now, there are plenty of taxis here, but you usually see black cabs in London, and even there, you don't see as many as you used to. I had seen them in other cities, but as far as I can remember never in our town. I always loved black cabs since I first saw them for the first time as a child, back in the late eighties, I thought they looked like the quintessential English vehicle. They are taxis with a certain style. The driver didn't seem to know our town one bit, he had his mobile in his hands giving descriptions of what he saw. I guess he probably dropped a client picked in London and he was trying to find the quickest way back to the city. I wonder what errand brought him here and who was the client who paid the expensive fare. Because London is fairly close, but not that close, especially by car. And this begs another question: why pay a black cab instead of, well, anything else?