Engine cleaners preparing a King Class 4-6-0 locomotive number 6008 "King James II", 1954. The locomotive had been built by the Great Western Railway in 1928.
Steam locomotives quickly got covered in the soot and ash from their coal fires and needed cleaning far more frequently than electric or diesel locomotives. It was hard and filthy work done by the lowest grade of engine crew.
Modern diesel and electric locomotives are usually cleaned in automated washing plants.
"King James II" was withdrawn from British Railways service in 1962.