High Quality Content by WIKIPEDIA articles! The Standard class 6, otherwise known as the Clan Class, was a class of 4-6-2 Pacific tender steam locomotive designed by Robert Riddles for use by British Railways. Ten locomotives were constructed between 1951 and 1952, with a further 15 planned for construction. However, due to acute steel shortages in Britain, the order was continually postponed until it was finally cancelled on the publication of the 1955 Modernisation Plan for the re-equipment of British Railways.