Kathleen Maria Margaret Archer (née Sissmore) MBE was the first female officer in Britain's Security Service, MI5, and was still their only woman officer at the time of her dismissal for insubordination in 1940. She had been responsible for investigations into Soviet intelligence and subversion. She then joined the Secret Intelligence Service (MI6), but when Kim Philby, later to be exposed as a double agent, became her boss he reduced her investigative work because he feared she might uncover his treachery.