"The volume begins with a series of short essays covering general trends in design development, whilst the main body of the volume covers individual classes. For each class there is a small table containing some principal dimensions and paragraphs of text, covering an introduction, renumbering, key changes in the development of the class and information on withdrawal. The volume concludes with appendices covering the development and types of standard boilers, the various numbering schemes used by the GWR, the arcane subject of locomotive diagrams and lot numbers, and a short reference on the many lines the GWR engulfed." -- from jacket