hatfield is of saxon origin. hatfield house, home of the marquess of salisbury, is the most important country house. aircraft were built from the 1930s when de havilland opened a factory until the 1990s when british aerospace closed it. aircraft design and manufacture employed more people there than any other industry. hatfield was one of the post-war new towns built around london. it has modernist architecture from the period. the university of hertfordshire is based there.