Sir Michael Hanley (1918–2001) served as an officer of the Royal Artillery during the Second World War. He became the Assistant Military Attaché in Budapest in 1946. He joined the Security Service in 1948.

In 1971, he became the Deputy Director General and was promoted to Director General the following year. During his time in office, he faced a difficult relationship with the Prime Ministers of the day. Harold Wilson wrongly suspected MI5 of plotting against him (see "The Wilson Plot") and James Callaghan decided to appoint a successor from outside the Service.