This is the tenth book by David Maidment in the Locomotive Portfolio' series and covers the large number of designs from 1860 onwards of 0-6-0 saddle tanks built for both the Great Western Railway and the independent railway companies in South Wales, most of which were converted to pannier tanks in the Churchward and Collett eras as they were reboilered with raised Belpaire fireboxes between the early 1900s and the late 1920s. As well as the Armstrong and Dean engines, the book goes on to describe the design, construction and operation of the largest class of steam engines built in the UK in the last century - Collett's familiar 57XX class, examples of which were still being built after nationalisation. Collett also designed pannier tank engines for branch passenger and freight work - the 54,64 & 74XX series, and Hawksworth continued the GW tradition with a tapered boiler version, the 94XX, after the Second World War as well as the light 16XX and the outside cylinder Walschaerts valve geared 15XX. This is a very comprehensive book covering so many classes, valuable for the modeller, and has over 400 photographs, over 50 in colour.