Grace's Guide is the leading source of historical information on industry and manufacturing in Britain. This web publication contains 126,824 pages of information and 199,901 images on early companies, their products and the people who designed and built them.
Late 1840s The Great Northern Railway employed a leading railway contractor, Thomas Brassey, to build the southern section of the line, including the Digswell viaduct, which was designed by Joseph Cubitt, the railway's chief engineer, on the lines of a Roman aqueduct.
The viaduct has 40 arches each spanning 9.1 metres across the Mimram Valley and was completed in 1850 using 16,000 (?) bricks all made on site. Another source quotes 5,000,000 bricks with an extra 1,181,000 bricks added in the 1930s to provide an outer skin of harder blue facing bricks.