On his father's death in 1949 he succeeded to the title Viscount Runciman of Doxford (created in 1937).
After graduating from Cambridge, Runciman joined the family shipping business, later becoming chairman of the company.
Post-war, Runciman served on many business and public organisations mainly related to shipping and air transport.
He was a Trustee of the National Maritime Museum at Greenwich from 1955, acting as chairman from 1962 to 1972.
Runciman married novelist Rosamond Nina Lehmann in 1923.