My classes on 42nd and 5th Avenue today ended early, so at the time the steam pipe exploded on 41st and Lexington at 5.57pm, killing at least one poor bystander and injuring 20 others, I was back in Brooklyn, striding energetically around the “green zone” of Prospect Park.

It was shocking to see the footage of the explosion, people running terrified away from the smoke in all directions, not knowing the cause of the noise and eruptions. A taste, however faint, of the confusion and mayhem that gripped the entire city almost six years ago. The ripples of fear persist: Mayor Bloomberg’s first public announcement was to reassure the public that the explosion was “nothing more than a failure of infrastructure”, that it was not an act of terrorism.