In the past I have found a metal outside bulkhead light earthed by a wire connected to a steel screw and washer that was just screwed into the brick wall below the light.
Yesterday I came upon a 50s/early 60s installation with no earthing at lighting points. Some brass plated light switches had been added by the previous owner. A sticker on the back of the brass switches said that they must be earthed, so the installed had amateurishly connected a wire from the brass plates to the central back box securing screw. The metal back boxes were unearthed though.
Z.
