His family moved to Albany, Western Australia, in 1912, but returned to Scotland in 1915 before going back to Australia in 1919.
Runciman attended Scotch College, Perth, and subsequently won a scholarship to the Royal Military College, Duntroon, although he did not pursue a military career.
Before entering politics, he was a farmer, spending periods at Wilga (1927 to 1948), Boyup Brook (1948 to 1952), and North Dandalup (from 1952).Runciman entered parliament at the 1962 Murray by-election, which was caused by the resignation of Sir Ross McLarty (a former premier).
He was re-elected three more times (in 1965, 1968, and 1971) before leaving parliament at the 1974 election.
Runciman died in Pinjarra in December 1981, aged 74.