The story of O V Bulleid''s ''Leader'' class is one that simply refuses to lie down, continuing to be a source of debate and controversy. Was this the great innovation that would have taken the steam locomotive to unheard of levels of sophistication and efficiency, or a folie de grandeur on the part of an undoubtedly creative, charismatic yet maverick engineer, which should never have been countenanced or financed by his superiors? Seventy years after the last examples of these ill-fated locomotives were scrapped, the controversy surrounding them still rumbles on and fascination with the project among railway enthusiasts is unabated.Having written previously on the subject, author Kevin Robertson has continued his research into the ''Leader'' class and unearthed much new material from a variety of sources which is presented here for the first time. Whilst not likely to have changed the end result, much new light is shed as to how that decision was arrived at. New sources have been explored that were not available previously and these add greatly to our understanding of how the project was managed, adding flavour and at times even comedy to the events recounted.