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The agency that would become MI5, Britain's domestic counter-intelligence service, employed just 17 staff in 1914, but by the end of the first world war that number had swelled to 850, including a number of female administrators.

- Esther Addley

While valuable for managing the card index records, noted Edith Lomax, the controller of women staff in 1918, only women under 30 should be recruited "on account of the very considerable strain that was thrown on [their] brains".

The merits of female intelligence staff remained a topic of debate within the agency. In 1945, Maxwell Knight, the leading agent-runner between the wars and reputedly the model for James Bond's M, said that while some believed women could not make suitable agents due to being "ruled by their emotions, and not their brains", "the emotional make-up of a properly balanced woman can very often be utilised in investigation... given the right guiding hand".

He might have looked to the organisation's early history during the first world war, when boy scouts were initially enlisted to run minor errands, only to be replaced by girl guides when they proved to be more reliable.