Early twentieth century offices and laboratory by Dunn and Watson, comprising the world's first purpose built radio factory. The Marconi Works at New Street, Chelmsford, were designed and erected in 1912. They replaced the much smaller works at Hall Street, chelmsford, which had become inadequate for the needs of the growing company. New Street was the first purpose-built radio factory in the world and ultimately became the Marconi Company headquarters.

From conception to completion, the project took only 17 weeks. Built on part of the old Essex Cricket Ground, the new works were modern and equipped with the latest tools and laboratories. The changeover between Hall St. and New St. happened in just one weekend. The Works were ready for inspection in June by the suitably impressed International Radiotelegraphic Conference delegates on 22 June 1912.

On 15 June 1920, New Street was host to Britain's first advertised public broadcast programme, a song recital by Dame Nellie Melba. A blue plaque commemorating this event is located on the front elevation of this listed building.

Marconi Defence Systems, the successor company, was broken up in 2001. The New Street site was taken over by Selex Communications. Its own move to Basildon was announced in 2005 and the site is due to be redeveloped although it is understood that its historical past will be fully considered in the plans for the site.