 Warburg died of heart failure at University College Hospital, London, on 25 May 1981, at the age of 82.Warburg started his publishing career in 1922, as an apprentice at Routledge & Sons, where he came under the tutelage of William Swan Stallybrass, a man he regarded as "the greatest scholar-publisher of his day".After Stallybrass died in 1931 Warburg became increasingly dissatisfied with Routledge and in 1935 he was dismissed.