During the early part of the 20th century, Great Baddow grew through ribbon development towards Chelmsford and Galleywood. In 1936, Marconi's Wireless Telegraph Company opened the Marconi Research Laboratory in Great Baddow (now BAE Systems Applied Intelligence Laboratories), bringing together their various radio, television and telephony research teams in a single location. As the electronics industry developed, the campus expanded during the 1940s and 1950s to include research into radar, general physics, high voltage, vacuum physics and semiconductors. Great Baddow expanded considerably in the 1950s with the construction of Rothmans Estate, which provided housing for workers at Marconi's and English Electric Valve Company in Chelmsford. The village has continued to expand over subsequent years.