As the Cold War came to an end, terrorist threats from Northern Ireland and states such as Colonel Qadhafi's Libya became priorities for MI5. Major reforms were put in place and the Service gained its first female Director General. The rise of Islamist terrorism at the end of the 1990s, culminating in the 9/11 attacks in 2001, led to major changes in the way MI5 operated.
How MI5 tackled the threats from the Provisional IRA and state-sponsored terrorism
How MI5 adjusted to a new era of counter-terrorism work
The story of MI5's transition from counter-espionage to counter-terrorism
MI5 and the response to the threat of terrorism from extremist Islamist groups