This photo took 25 years to create. I was at the National Gallery 25 years ago, and tried to capture a photo from this position and wasn't able to. Went back a few years ago and waited in the same place. I took about a dozen photos before I saw the couple coming down the escalator. They were very "affectionate" as they descended, and I was able to catch them in the middle of a kiss. It was shear serindipity that all the other elements fell into place. One of my all time favorite B&W images.