The second woman to head MI5 takes over as the director-general today with the domestic security agency facing one of the most difficult periods in its history.
Eliza Manningham-Buller succeeds Sir Stephen Lander, who stepped down this year. The only other female leader of MI5 has been Stella Rimington, whose tenure created some controversy.
Mrs Manningham-Buller is the 52-year-old daughter of a former conservative attorney-general and a schoolmate of Princess Anne at Benenden.
Her appointment comes at a time when MI5 is striving for more public transparency and accountability.