[4] He was educated at Eton College, an all-boys public school in Berkshire, where he won the Newcastle Scholarship.
In 2020, Runciman co-founded the Cambridge Centre for the Future of Democracy, a research institute dedicated to the exploration of innovative approaches to the study of democratic governance worldwide.
[13] The Confidence Trap: A History of Democracy in Crisis from World War I to the Present (2013) lays out his theory of the threat of democratic overconfidence.
Andrew Rawnsley in The Guardian wrote that the book left him "feeling more positive than I thought I would be" [17] From 2016 to 2022, Runciman hosted a podcast called Talking Politics with professor Helen Thompson.
The podcast convened a panel of academics from the University of Cambridge and elsewhere to speak about current affairs and politics.
[19] Oliver Eagleton, writing in the New Statesman, said of it "There [Runciman] reflected on current affairs in his reassuring Eton baritone: parsing the headlines, never taking too strident a position, throwing softball questions to his guests ... and recycling conventional north London wisdom".
[4][23] Since 2021 he has been married to psychotherapist Helen Runciman (née Lyon-Dalberg-Acton), daughter of academic Edward Acton.