Stanley Keith Runcorn was born in 1922 in Southport, Lancashire, the son of a monumentalmason of staunch Congregationalist persuasion. He was educated at the King George VGrammar School, where his strongest subjects were history and mathematics. When in thesixth form his headmaster persuaded him to take science subjects, and he was subsequentlyawarded a State Scholarship to study at Cambridge University. At an early age his father hadtaken him to a small local observatory, encouraging his interest in astronomy. On the sportingside, in spite of his later interest in rugby he refused to play the game at school and insteadconcentrated on swimming. Under his captaincy his house regularly won the swimming trophy.
Runcorn showed an early interest in religious and cultural matters, which was to stay with him throughout his life. He attended a Methodist Sunday school and for some time provided a Sunday evening service for his sister and grandmother while his parents attended church. He read extensively and went to London on his own, visiting museums and architectural landmarks. Later, while at Cambridge, he developed a love of music.
In 1940 he entered Gonville and Caius College at Cambridge to read electrical engineering. After graduating in 1943 he commenced research at the Royal Radar Establishment (RRE), remaining there until the end of the war. During his time at the RRE he was confirmed into the Church of England.