The Berkeley Square Ball used to be held annually for 'the beautiful people' in the middle of Berkeley Square in London.
Berkeley Square Ball 1983
Prince Michael of Kent
Princess Michael of Kent
Diana Dors and son, Jason
One particular problem that you can have with this type of photography is that you frequently have to react extremely quickly to get a picture without time to focus or compose the picture properly. The usual way around the focus problem was to use a wide angle lense (typically 24mm) with a long depth of field. This meant that you could concentrate on the composition and let the focus take care of itself.
An example of this is the photo of Diana Dors in the Berkeley Square Ball gallery. I happened to notice a couple of figures walking away in the gloom and banged of a shot before they disappeared. It was a miracle that the light from the flashgun carried far enough. The quality is not up to a standard that I would normally regard as acceptable. I have only included it because it was the only time I ever saw her as unfortunately she died a few months later so I never got another chance. I have shown it below along with the full frame photo from which it was taken and you can see that the finished result was only about 5% of the original picture.