Following a series of experiments relating to the steaming capabilities of 7018 " Drysllwyn Castle " , an engine with a poor reputation and regarded as being an indifferent steamer , and following the locomotive's subsequent evaluations undertaken by Swindon Works in 1956 , it was 4090 " Dorchester Castle " which in April of 1957 became the first " Castle " to be fitted with the double chimney which had proved so successful during those earlier trials conducted with 7018 .
" Dorchester Castle " , therefore , became the forerunner of the class to gain a new lease of life , despite her age , and she lasted in service until June of 1963 .
At the date of this image she would have been allocated to Shrewsbury , but spent her last months at Cardiff East Dock Depot .