After a short while, the second car (apparently assuming that the car in front was waiting to turn right) honked its horn. This produced no action (I think because the car in front was actually waiting to turn left), so it honked again. And again. And again.
The car in front started trying to maneuver to let the other car by, but there wasn't much room for such things, so the other car continued to honk.
My friends and I made some sarcastic comments about the situation, and I started to walk over to try to intervene in some ill-advised way, although I'm not quite sure what I was going to do -- possibly try to explain that I thought the car in front was waiting to turn left and not right. But it didn't come to that, for as I stepped into the street a policeman on a horse galloped up and had a little shouted conversation with the honker.
Policeman: "Why are you honking your horn?"
Driver: [something I didn't hear distinctly]
Policeman: "Why are you in such a hurry, then?"
Driver: [something else I didn't catch]
Policeman: "There's no call to be honking your horn like that. That's a $75 ticket. You shouldn't be doing that."
At around this point, the light changed, the car in front drove away, and the policeman rode away also. The guy who had been honking drove off and took his right turn also, taking the opportunity to give the policeman a little piece of his mind, such as it was:
Driver: "Motherfucking horse cop pussy!"
Shortly after that we were joined by our friends and went on our way.