Its a very cliched idea, using the characteristics of a fast lens with good bokeh to make an image.
The light was good, the scene ok, nice but not spectacular, the white railings disappearing into the distance is what interested me.
I thought wide open with a blurred background it would make an interesting image. The colour was not something I thought about and after looking at the colour image afterwards I thought the black & white image may make a stronger image.