Bull worked for the Fincancial Times, McGraw-Hill World News and for the Director magazine, of which he was Editor-in-Chief until 1984. He was appointed Director of the Anglo-Japanese Economic Institute in 1986. He was a director of Central Banking Publications and the founder and publisher of the quarterly publications Inside Japan and International Minds.
He translated six volumes for the Penguin Classics series: Benvenuto Cellini's Autobiography, The Book of the Courtier by Castiglione, Vasari's Lives of the Artists (two volumes), The Prince by Machiavelli and Pietro Aretino's Selected Letters.
He was also Consultant Editor to the Penguin Business Series.
His other books include Vatican Politics; Bid for Power (with Anthony Vice), a history of take-over bids; Renaissance Italy, a book for children; Venice: The Most Triumphant City; and Inside the Vatican.