This book establishes the place of Hush Hush in British Railway history. The need for efficiency is explored and in doing so the reason for the machine's existance is explained. The day to day experiences of North Road Works in respect to the water tube and compound locomotive is chronicled and hence the problems with this project and solutions are finally placed into the public domain. The reasons for the termination of the experiment are considered. The book concludes with a brief look at the work of Chapelon suggesting that more could have been made of this and other experiments.