Clerestory coaches were built in the days of oil and gas lighting, the clerestory providing additional clearance and ventilation for the large lamps and burners in addition to allowing more light into the coaches during daytime. The development of smaller burners and electric lighting allowed simpler and cheaper to construct roof profiles to be used, but the distinguished looking clerestory coaches could still be found on secondary and seasonal train services until nationalisation.
This third class clerestory coach is painted in the lined and panelled livery applied by the GWR before WW1 and for a few years into the 1920s.