The 517 Class were small 0-4-2T tank engines designed by George Armstrong for local passenger work on the Great Western 
Railway. 144 were built at Wolverhampton Works  in 13 lots and were outshopped between 1868 and 1885. During the late 1880’s and early 1890’s most had their wheelbases lengthened to 15 foot 6 inches and from 1904 onwards several were converted to auto train working which scattered them over the system. When Charles Collett became CME, during 1924 he widened the tanks and provided a new cab with extended bunker which became the Swindon rebuild and outwardly looked very similar to the later 48xx class he designed in 1932. The last of the class 1159 was withdrawn in August 1947 just missing out on nationalization. All members of the class were disposed of with none making it into preservations.