‘A foggy day in London town,’ croons Fred Astaire in the 1937 musical comedy A Damsel in Distress, puffing nonchalantly on a cigar as he wanders through a wood that has already been half obliterated by belching Hollywood smoke machines. Today Gershwin’s lyrics conjure up a nostalgic vision of life in the city, involving pale fingers of fog wrapping themselves around lamp posts and the muffled clop of hooves on cobbles.