Published in 2007 with 408 pages of text, including 43 pages of full colour maps.  These are two of London's "Home Counties" which are now given over mostly to housing. Long term industrial activity in Hertfordshire comprised of factories in Watford, and other engineering works around Potters Bar and Hitchin. There were many gasworks, factories and power station in the Lea Valley from Tottenham to Brimsdown. There were also extensive sand and gravel pits. Middlesex had fewer industrial locomotives sites  but it did include the major plant depot owned by Sir Robert McAlpine & Sons Ltd. The book also lists the narrow gauge plant of George Bungey and M.E. Engineering.  The book contains a comprehensive selection of 64 interesting black and white photographs.