Patrick Dalmahoy Nairne was born in London, 15 August 1921, the son of Charles Sylvester Nairne and Edith Dalmahoy Nairne (née Kemp). He was educated at Hordle House School, 1930-5, Radley College, 1935-40, and University College, Oxford, 1940 and 1946-7. He married Penelope Chauncy Bridges in 1948, with whom he had three sons and three daughters.

During the Second World War, he served with the Seaforth Highlanders, 1941-5; saw action in North Africa, Sicily, and North West Europe; and was awarded the Military Cross, 1943. On completing his degree, he entered the Civil Service and was posted to the Admiralty, 1947-63, where he was Private Secretary to the First Lord of the Admiralty, 1958-60, and Assistant Secretary, 1960-63. After the reorganisation of the Service Departments into one Ministry of Defence, he became Private Secretary to the Secretary of State for Defence, 1965-7, and then Assistant Under-Secretary, 1967-70, and Deputy Under-Secretary, 1970-3. He was appointed Second Permanent Secretary in the Cabinet Office, where he headed the Civil Contingencies Unit, 1973-5, and Permanent Secretary in the Department of Health and Social Security, 1975-81.

After his retirement from the Civil Service, he became Master of St Catherine's College, Oxford, 1981-8, and Chancellor of Essex University, 1983-97.

He was also a member of the Falkland Islands Review Committee (the Franks Committee), 1982; a Government Monitor in Hong Kong, 1984; Chairman of the Nuffield Council on Bioethics, 1991-6; and Chairman of the Commission on the Conduct of Referendums, 1996. He became involved with the campaign for the repeal of Section 2 of the Official Secrets Act and for a Freedom of Information Act.

He was appointed CB, 1971, KCB, 1975, and GCB, 1981, and became a member of the Privy Council, 1981. He was also an Honorary Fellow of University College, Oxford, from 1981, and St Catherine's College, Oxford, from 1988.

He died in Oxfordshire on 4 June 2013.