Bernard Arthur Owen Williams was born in Westcliff, Essex, on Sept. 21, 1929, the son of Owen Pasley Denny Williams, an architect and surveyor, and Hilda Amy (Day) Williams, a secretary. He attended Chigwell School and went on to read classics at Balliol College, Oxford, where he was already considered a prodigy. He later was given many honorary degrees but did not earn a doctorate. According to a profile in The Guardian of London by Stuart Jeffries, Sir Bernard's mentor at Oxford, Gilbert Ryle, later said of him, ''He understands what you're going to say better than you understand it yourself, and sees all the possible objections to it, all the possible answers to all the possible objections, before you've got to the end of your sentence.''

According to a Guardian obituary by Jane O'Grady, Sir Bernard neglected the historical aspect of the classics to the degree that he claimed to have used part of his history finals' time to learn history; he arrived 29 minutes late for the exam wearing a white magnolia in his buttonhole.

He graduated with a congratulatory first-class degree, a highly unusual honor in which the examining professors ask no questions about the candidate's written work but simply stand and applaud.

Sir Bernard then did his national service in the Royal Air Force and excelled as a fighter pilot. He later said that the year he spent flying Spitfires in Canada was the happiest of his life. While on leave in New York City, he went out with Shirley Brittain, later a prominent British politician, who was then studying at Columbia University. He had known her when they were students in England, and they married in 1955. The marriage ended in 1974, The Daily Telegraph reported. They had a daughter, Rebecca, who survives him along with his second wife, Patricia Law Skinner, whom he married in 1974 when she was Cambridge University Press's philosophy editor, and their sons, Jacob and Jonathan.

After returning to England at age 22 he was made a fellow at All Souls but left Oxford. first for University College, London, and later Bedford College (now defunct), reportedly to serve the political ambitions of his wife, who later became Baroness Williams of Crosby, a leader of the Liberal Democrats in the House of Lords. The couple and their newborn daughter lived in a large house in Kensington with the literary agent Hilary Rubinstein, his wife, their four children and various boarders, an arrangement that remained amicable for 17 years.