Maurice Oldfield was the son of a tenant farmer in Derbyshire. He studied medieval history at Manchester University and during the Second World War served in the South Staffordshire Regiment. Later he was transferred to the Intelligence Corps.
After the war Oldfield joined MI6, the Secret Service with responsibility for counter-espionage outside Britain. He worked in London before being posted to the Far East and Washington.
He made gradually progress under Sir Dick White and in 1973 replaced Sir John Rennie as Director-General of MI6. He held the post under Edward Heath, Harold Wilson and James Callaghan before retiring in 1978.
In 1979 the new prime minister, Margaret Thatcher, asked Oldfield to coordinate security and intelligence in Northern Ireland. He left this post in 1980 after his positive vetting clearance was withdrawn. Apparently this was because he admitted that "from time to time engaged in homosexual activities."
He was reputedly the model for John le Carré's fictional character George Smiley.