Philip S. Bagwell 
Railway Clearing House [PDF ebook] 
In the British Economy 1842-1922

Originally published in 1968, and using official records, this book charts the history of the Railway Clearing House and shows the vital role it played in the development of British railways and the growth of the economy. The Clearing House established a common classification of goods; standardized signalling systems and telegraphic codes among the 120 railway companies which operated in Britain before the First World War. It was the nerve centre of the railway for nearly a century and at one time more than 2, 500 clerks were employed in its huge offices near Euston Station in London.