From Times Online:
In the early days of MI5, most women recruits were recommended by existing members of staff. When, after 1914, demand outpaced supply, the service turned to Cheltenham Ladies College and other leading girls’ public schools and to St Hugh’s and Somerville Colleges at Oxford. Women played a more important role in the security service than in any other wartime government department, maintaining its registry and letter checks which were kept up to date by 130 women clerks. By early 1917, MI5’s Central Registry contained 250,000 cards and 27,000 files on its chief suspects.
During the early months of the war, the registry was “almost overwhelmed” by “the tidal wave of documents” which descended on it. When Hilda Cribb (who in 1920 was to become controller of women staff) began work in the registry in February 1915 she found unfiled papers stacked on filing cabinets. All this changed with the appointment of Edith Annie Lomax as lady superintendent. She proved to be one of the ablest administrators in service history, later becoming the first female member of staff to be appointed MBE (subsequently upgraded to OBE).
The biggest obstacle to female promotion was the general conviction throughout the British intelligence community that women were unsuitable for agent-running. The only woman selected for the first agent-running training course in 1973 was Stella Rimington, later the first female DG. Rimington believed that, in the aftermath of “The Women’s Revolt”, management “were genuinely surprised at the strength of feeling and sufficiently concerned that so many of their good female staff, essential to the running of the service, appeared to be disgruntled, that the policy was changed”. A number of female assistant officers, Rimington among them, were promoted to full officer rank and women began, like men, to be recruited at officer level.
Over the next decade in the recruitment of female officers the service moved ahead of much of Whitehall and most employers in the private sector. By the early 1990s some 40 per cent of its officers were women.