There are several "Nominal Rolls" which purported to list the total membership of the Establishment on 5th August 1940, early 1942 and August 1942 after our move to Malvern.
There is also a series of photographs of the organisation board Mr
A.P. Rowe the Superintendent used to have on the wall in his
office - "Director's Charts" . This consisted of magnetic nameplates on a steel panel that his office staff were supposed to keep up to date. It mainly showed scientific and technical staff and as numbers increased junior members were omitted.
I mainly used the March 1942 photograph to extract the names of people I tried to persuade to write their memories of that time. Sidney Jefferson supplied the information on the functions of the various groups.
Staff numbers had increased to about 2000 when we moved to Malvern and to about 3,500 plus many Service personnel by the end of the war.