Butler studied at Pembroke College, Cambridge, starting in October 1921, initially reading Medieval and Modern Languages. He soon became active in student politics, being elected to the Committee of the Cambridge Union Society by the end of his first year. At the end of his second year, he was elected Secretary for Michaelmas (autumn term) 1923 at his second attempt, by the narrow margin of 10 votes out of 500. At that time, Secretary was the only office normally contested, putting him on track to be Vice-President for Lent 1924 and President for Easter (summer term) 1924. At the end of his second year (June 1923), he achieved a First in French Part I and was awarded an £80 scholarship to supplement his £300 parental allowance (approximately £4,000 and £15,000 at 2014 prices).