The Women's Auxiliary Air Force was created from the Auxiliary Territorial service. One job was so secret that not many knew about it – Clerk Special Duties – and included training as Radar Operators, Filter Room Plotters and Tellers. The Filter Room team constantly upgraded the picture, and the information they produced was relayed to Group and Sector Operations Rooms and the Observer Corps. Throughout 1940, WAAFs were employed on front-line Radar Units and at Fighter command, Group and Sector Operations Rooms, and within the Filter Centre based at RAF Bentley Priory, Stanmore.