"Haven of Rest" by Douglas Gurton says
"LLANSTEPHAN CASTLE was later joined by two fairly modern cargo ships of the same company, the BRATTON CASTLE and SANDOWN CASTLE. These were known as "black ships" being painted black in contrast to the lavender grey hulls of the passenger liners.
See DJG_SHP Scrapped 1950
Mid Essex WSS - Lloyds List: arrived 7 Feb 1923 sailed 18 Jun 1923