GWR County No 1000 County of Middlesex, fitted with a double chimney, waits to leave Paddington with a down express on July 8, 1952.

Peter Kerslake says "The pioneer of its class, has BR lined black livery awas the only 'County' to have a double chimney and blast pipe until 1956 when, following tests with this engine and 1009 County of Carmarthen all the class were equipped, but with double chimneys of a less attractive design."
Photo: John P Wilson/Rail Archive Stephenson