The Great Western Castles were one of the most successful locomotive designs of the twentieth century in terms of both performance and efficiency. Designed by Charles Collett in 1923, based on the 1907 Churchward Star' class, 155 were constructed almost continuously, apart from the war years, between 1923 and 1950, in addition to fifteen rebuilt Stars' and one rebuilt from the Great Bear pacific. Many were modernised with increased superheat and double-chimneys in the late 1950s and the class continued to be the mainstay of all Western Region express passenger services to the West Country, South Wales, Gloucestershire, Herefordshire and the West Midlands until replaced by the WR diesel hydraulic fleet in the early 1960s. This book covers their design in a chapter written by Bob Meanley, who masterminded the restoration at Tyseley Works of the Castles Earl of Mount Edgcumbe and Clun Castle, and their history, operation and performance from the high speed of the 1930s through to their rejuvenation in the 1950s, leaving experience of their last years and preservation to another volume. David Maidment had close experience of the class when working at Old Oak Common between 1957 and 1962 and includes his personal experiences there and on the road from his first encounter with one as a six-year old boy. The book includes 350 photographs, some 40 in colour, and 23 detailed Swindon technical drawings.